here is the logs 

Caught unhandled exception with ID d016c053-6794-4dfb-9cbe-8618d701d91a java.lang.IllegalArgumentException: Illegal pattern character 'I' at java.base/java.text.SimpleDateFormat.compile(Unknown Source) at java.base/java.text.SimpleDateFormat.initialize(Unknown Source) at java.base/java.text.SimpleDateFormat.<init>(Unknown Source) at java.base/java.text.SimpleDateFormat.<init>(Unknown Source) at PluginClassLoader for robot//hudson.plugins.robot.graph.RobotBuildLabel.formatBuildLabel(RobotBuildLabel.java:23) at PluginClassLoader for robot//hudson.plugins.robot.graph.RobotBuildLabel.<init>(RobotBuildLabel.java:17) at PluginClassLoader for robot//hudson.plugins.robot.graph.RobotGraphHelper.createTestResultsGraphForTestObject(RobotGraphHelper.java:88) at PluginClassLoader for robot//hudson.plugins.robot.model.RobotTestObject.doGraph(RobotTestObject.java:267) at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(Unknown Source) at org.kohsuke.stapler.Function$MethodFunction.invoke(Function.java:416) at org.kohsuke.stapler.Function$InstanceFunction.invoke(Function.java:429) at org.kohsuke.stapler.Function.bindAndInvoke(Function.java:211) at org.kohsuke.stapler.Function.bindAndInvokeAndServeResponse(Function.java:138) at org.kohsuke.stapler.MetaClass$11.doDispatch(MetaClass.java:644) at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:61) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:827) Caused: javax.servlet.ServletException at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:878) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:791) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.MetaClass$9.dispatch(MetaClass.java:548) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:827) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.MetaClass$9.dispatch(MetaClass.java:548) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:827) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:327) at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:61) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:827) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.MetaClass$4.doDispatch(MetaClass.java:327) at org.kohsuke.stapler.NameBasedDispatcher.dispatch(NameBasedDispatcher.java:61) at org.kohsuke.stapler.Stapler.tryInvoke(Stapler.java:827) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:965) at org.kohsuke.stapler.Stapler.invoke(Stapler.java:747) at org.kohsuke.stapler.Stapler.service(Stapler.java:253) at Jenkins Main ClassLoader//javax.servlet.http.HttpServlet.service(HttpServlet.java:590) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:764) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$ChainEnd.doFilter(ServletHandler.java:1665) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:163) at PluginClassLoader for sse-gateway//org.jenkinsci.plugins.ssegateway.Endpoint$SSEListenChannelFilter.doFilter(Endpoint.java:248) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at PluginClassLoader for audit-trail//hudson.plugins.audit_trail.AuditTrailFilter.doFilter(AuditTrailFilter.java:89) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at PluginClassLoader for blueocean-web//io.jenkins.blueocean.ResourceCacheControl.doFilter(ResourceCacheControl.java:134) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at PluginClassLoader for blueocean-jwt//io.jenkins.blueocean.auth.jwt.impl.JwtAuthenticationFilter.doFilter(JwtAuthenticationFilter.java:60) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at PluginClassLoader for monitoring//net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:239) at PluginClassLoader for monitoring//net.bull.javamelody.MonitoringFilter.doFilter(MonitoringFilter.java:215) at PluginClassLoader for monitoring//net.bull.javamelody.PluginMonitoringFilter.doFilter(PluginMonitoringFilter.java:88) at PluginClassLoader for monitoring//org.jvnet.hudson.plugins.monitoring.HudsonMonitoringFilter.doFilter(HudsonMonitoringFilter.java:121) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at PluginClassLoader for modernstatus//org.jenkinsci.plugins.modernstatus.ModernStatusFilter.doFilter(ModernStatusFilter.java:50) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at jenkins.util.HttpServletFilter$1.doFilter(HttpServletFilter.java:76) at hudson.util.PluginServletFilter$1.doFilter(PluginServletFilter.java:160) at hudson.util.PluginServletFilter.doFilter(PluginServletFilter.java:166) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at jenkins.ErrorAttributeFilter.doFilter(ErrorAttributeFilter.java:29) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at hudson.security.csrf.CrumbFilter.doFilter(CrumbFilter.java:160) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:94) at jenkins.security.AcegiSecurityExceptionFilter.doFilter(AcegiSecurityExceptionFilter.java:52) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at hudson.security.UnwrapSecurityExceptionFilter.doFilter(UnwrapSecurityExceptionFilter.java:54) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:126) at org.springframework.security.web.access.ExceptionTranslationFilter.doFilter(ExceptionTranslationFilter.java:120) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at org.springframework.security.web.authentication.AnonymousAuthenticationFilter.doFilter(AnonymousAuthenticationFilter.java:100) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:110) at org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter.doFilter(RememberMeAuthenticationFilter.java:101) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:227) at org.springframework.security.web.authentication.AbstractAuthenticationProcessingFilter.doFilter(AbstractAuthenticationProcessingFilter.java:221) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at jenkins.security.BasicHeaderProcessor.doFilter(BasicHeaderProcessor.java:97) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:117) at org.springframework.security.web.context.SecurityContextPersistenceFilter.doFilter(SecurityContextPersistenceFilter.java:87) at hudson.security.HttpSessionContextIntegrationFilter2.doFilter(HttpSessionContextIntegrationFilter2.java:63) at hudson.security.ChainedServletFilter$1.doFilter(ChainedServletFilter.java:99) at hudson.security.ChainedServletFilter.doFilter(ChainedServletFilter.java:111) at hudson.security.HudsonFilter.doFilter(HudsonFilter.java:172) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at org.kohsuke.stapler.compression.CompressionFilter.doFilter(CompressionFilter.java:53) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at hudson.util.CharacterEncodingFilter.doFilter(CharacterEncodingFilter.java:86) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at org.kohsuke.stapler.DiagnosticThreadNameFilter.doFilter(DiagnosticThreadNameFilter.java:31) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at jenkins.security.SuspiciousRequestFilter.doFilter(SuspiciousRequestFilter.java:38) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.FilterHolder.doFilter(FilterHolder.java:202) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler$Chain.doFilter(ServletHandler.java:1635) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:527) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:131) at Jenkins Main ClassLoader//org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:569) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:122) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:223) at Jenkins Main ClassLoader//org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:1580) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.nextHandle(ScopedHandler.java:221) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:1384) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:176) at Jenkins Main ClassLoader//org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:484) at Jenkins Main ClassLoader//org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1553) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.nextScope(ScopedHandler.java:174) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:1306) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:129) at Jenkins Main ClassLoader//org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:122) at Jenkins Main ClassLoader//org.eclipse.jetty.server.Server.handle(Server.java:563) at Jenkins Main ClassLoader//org.eclipse.jetty.server.HttpChannel$RequestDispatchable.dispatch(HttpChannel.java:1598) at Jenkins Main ClassLoader//org.eclipse.jetty.server.HttpChannel.dispatch(HttpChannel.java:753) at Jenkins Main ClassLoader//org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:501) at Jenkins Main ClassLoader//org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:287) at Jenkins Main ClassLoader//org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:314) at Jenkins Main ClassLoader//org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:100) at Jenkins Main ClassLoader//org.eclipse.jetty.io.SelectableChannelEndPoint$1.run(SelectableChannelEndPoint.java:53) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.runTask(AdaptiveExecutionStrategy.java:421) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.consumeTask(AdaptiveExecutionStrategy.java:390) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.tryProduce(AdaptiveExecutionStrategy.java:277) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.run(AdaptiveExecutionStrategy.java:199) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.ReservedThreadExecutor$ReservedThread.run(ReservedThreadExecutor.java:411) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:969) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.doRunJob(QueuedThreadPool.java:1194) at Jenkins Main ClassLoader//org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1149) at java.base/java.lang.Thread.run(Unknown Source)

Also check my pipeline

pipeline {
    agent

    environment

    stages {
        stage('Publish Test Report') {
            steps {
                script {
                    echo "Variables:"
                    echo "${env.outputFileName}"
                    echo "${env.reportFileName}"
                    echo "${env.logFileName}"
                    echo "${env.otherFiles}"

                    // Configure Robot Framework plugin
                    robot(
                        outputPath: "./",   // Test directory
                        outputFileName: "${env.outputFileName}",
                        reportFileName: "${env.reportFileName}",
                        logFileName: "${env.logFileName}",
                        otherFiles: "${env.otherFiles}",
                        disableArchiveOutput: false,
                        enableCache: false,
                        onlyCritical: false,
                        passThreshold: 100,
                        unstableThreshold: 80,
                        overwriteXAxisLabel: "Test Report - Arch: ${env.ARCHITECTURE}"
                    )

                    echo "Completed | Publish Test Report"
                }
            }
        }
    }
}

Hi ayush9304,

Thanks for reporting this. I am able to reproduce this issue and I'll try to fix this as soon as possible.

This is caused due to the

overwriteXAxisLabel: "Test Report - Arch: ${env.ARCHITECTURE}"

in your pipeline. Removing this will make the plugin work and the graph is created normally. Currently the plugin is not parsing env vars when generating the graph, there's only two separate hard coded values:

        String pattern = format.replace("$build",""+run.number);
        pattern = pattern.replace("$display_name", run.getDisplayName());

As a workaround, you can change the build name into your desired build label and use "overwriteXAxisLabel: $display_name" in your build