There were errors checking the update sites: Signature verification failed in update site 'default' <a href='#' class='showDetails'>(show details)</a><pre style='display:none'>java.security.cert.CertificateExpiredException: NotAfter: Tue Nov 19 22:21:39 CET 2019<br> at sun.security.x509.CertificateValidity.valid(CertificateValidity.java:274)<br> at sun.security.x509.X509CertImpl.checkValidity(X509CertImpl.java:629)<br> at sun.security.provider.certpath.BasicChecker.verifyValidity(BasicChecker.java:190)<br> at sun.security.provider.certpath.BasicChecker.check(BasicChecker.java:144)<br> at sun.security.provider.certpath.PKIXMasterCertPathValidator.validate(PKIXMasterCertPathValidator.java:125)<br>Caused: java.security.cert.CertPathValidatorException: validity check failed<br> at sun.security.provider.certpath.PKIXMasterCertPathValidator.validate(PKIXMasterCertPathValidator.java:135)<br> at sun.security.provider.certpath.PKIXCertPathValidator.validate(PKIXCertPathValidator.java:233)<br> at sun.security.provider.certpath.PKIXCertPathValidator.validate(PKIXCertPathValidator.java:141)<br> at sun.security.provider.certpath.PKIXCertPathValidator.engineValidate(PKIXCertPathValidator.java:80)<br> at java.security.cert.CertPathValidator.validate(CertPathValidator.java:292)<br> at org.jvnet.hudson.crypto.CertificateUtil.validatePath(CertificateUtil.java:93)<br> at jenkins.util.JSONSignatureValidator.verifySignature(JSONSignatureValidator.java:85)<br> at hudson.model.UpdateSite.verifySignature(UpdateSite.java:253)<br> at hudson.model.UpdateSite.updateData(UpdateSite.java:217)<br> at hudson.model.UpdateSite.updateDirectlyNow(UpdateSite.java:188)<br> at hudson.PluginManager.checkUpdatesServer(PluginManager.java:1748)<br> at hudson.util.Retrier.start(Retrier.java:62)<br> at hudson.PluginManager.doCheckUpdatesServer(PluginManager.java:1719)<br> at jenkins.model.DownloadSettings$DailyCheck.execute(DownloadSettings.java:130)<br> at hudson.model.AsyncPeriodicWork$1.run(AsyncPeriodicWork.java:101)<br> at java.lang.Thread.run(Thread.java:748)<br></pre>