I have the same behavior with version 1.0.50 of the sync plugin.
Besides the secret issue, also BuildConfigs are not synced initially.

Update or new BuildConfigs will be created in Jenkins.

Version 1.0.49 still works. 
Breaking change was probably introduced in this commit: https://github.com/jenkinsci/openshift-sync-plugin/commit/d76165d9937e97cebd5b184d8f635b15c7c2cabf

Also tracking the issue on GitHub. Most people need pre 1.0.47 when the new method for getting resources was brought in. Weird that 1.0.49 works for you.

https://github.com/openshift/jenkins-sync-plugin/issues/392

Work to fix this issue will be tracked in https://bugzilla.redhat.com/show_bug.cgi?id=2024933

Same case here

Openshift version 4.8
Kubernetes version 1.21.1
Jenkins version 2.303.3

Secrets are not being syncd at all.

We're seeing this since last Openshift update to 4.8. Tried downgrading other plugins like kubernetes, kubernets-api, kubernetes-credential as found in other posts but nothing worked.

With 1.0.50, 1.0.51 and 1.0.52 obtaining same error:

2022-01-18 18:42:31 WARNING hudson.ExtensionFinder$GuiceFinder$FaultTolerantScope$1 error Failed to instantiate Key[type=io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration, annotation=[none]]; skipping this component
com.google.inject.ProvisionException: Unable to provision, see the following errors:
1) Error injecting constructor, java.lang.NoSuchMethodError: 'okhttp3.OkHttpClient io.fabric8.openshift.client.DefaultOpenShiftClient.getHttpClient()'
at io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration.<init>(GlobalPluginConfiguration.java:109)
1 error
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:52)
at com.google.inject.internal.SingletonScope$1.get(SingletonScope.java:145)
at hudson.ExtensionFinder$GuiceFinder$FaultTolerantScope$1.get(ExtensionFinder.java:441)
at com.google.inject.internal.InternalFactoryToProviderAdapter.get(InternalFactoryToProviderAdapter.java:41)
at com.google.inject.internal.InjectorImpl$2$1.call(InjectorImpl.java:1016)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1092)
at com.google.inject.internal.InjectorImpl$2.get(InjectorImpl.java:1012)
at hudson.ExtensionFinder$GuiceFinder._find(ExtensionFinder.java:401)
at hudson.ExtensionFinder$GuiceFinder.find(ExtensionFinder.java:392)
at hudson.ClassicPluginStrategy.findComponents(ClassicPluginStrategy.java:349)
at hudson.ExtensionList.load(ExtensionList.java:382)
at hudson.ExtensionList.ensureLoaded(ExtensionList.java:318)
at hudson.ExtensionList.iterator(ExtensionList.java:170)
at hudson.ExtensionList.get(ExtensionList.java:147)
at org.jenkinsci.main.modules.sshd.SSHD.get(SSHD.java:263)
at org.jenkinsci.main.modules.sshd.SSHD.init(SSHD.java:268)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:180)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1158)
at org.jvnet.hudson.reactor.Reactor$2.run(Reactor.java:214)
at org.jvnet.hudson.reactor.Reactor$Node.run(Reactor.java:117)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:68)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.lang.NoSuchMethodError: 'okhttp3.OkHttpClient io.fabric8.openshift.client.DefaultOpenShiftClient.getHttpClient()'
at io.fabric8.jenkins.openshiftsync.OpenShiftUtils.initializeOpenShiftClient(OpenShiftUtils.java:153)
at io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration.start(GlobalPluginConfiguration.java:128)
at io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration.configChange(GlobalPluginConfiguration.java:123)
at io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration.<init>(GlobalPluginConfiguration.java:111)
at io.fabric8.jenkins.openshiftsync.GlobalPluginConfiguration$$FastClassByGuice$$7bc306ea.newInstance(<generated>)
at com.google.inject.internal.cglib.reflect.$FastConstructor.newInstance(FastConstructor.java:40)
at com.google.inject.internal.DefaultConstructionProxyFactory$1.newInstance(DefaultConstructionProxyFactory.java:61)
at com.google.inject.internal.ConstructorInjector.provision(ConstructorInjector.java:105)
at com.google.inject.internal.ConstructorInjector.access$000(ConstructorInjector.java:32)
at com.google.inject.internal.ConstructorInjector$1.call(ConstructorInjector.java:89)
at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:115)
at hudson.ExtensionFinder$GuiceFinder$SezpozModule.onProvision(ExtensionFinder.java:568)
at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:126)
at com.google.inject.internal.ProvisionListenerStackCallback.provision(ProvisionListenerStackCallback.java:68)
at com.google.inject.internal.ConstructorInjector.construct(ConstructorInjector.java:87)
at com.google.inject.internal.ConstructorBindingImpl$Factory.get(ConstructorBindingImpl.java:267)
at com.google.inject.internal.ProviderToInternalFactoryAdapter$1.call(ProviderToInternalFactoryAdapter.java:46)
at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1103)
at com.google.inject.internal.ProviderToInternalFactoryAdapter.get(ProviderToInternalFactoryAdapter.java:40)
... 29 more

We're tracking the NoSuchMethod error in https://bugzilla.redhat.com/show_bug.cgi?id=2040810