Hi,
We've been seeing the exception below for a while now. Since upgrading to Jenkins 2.240 and Kubernetes Plugin 1.26 it has started to add a permanent notification every N minutes. When I logged in today, there were about 9480 notifications and it was keeping on adding new notifications. Those won't go away until you restart Jenkins. 
Failed to initialize Kubernetes secret providerio.fabric8.kubernetes.client.KubernetesClientException: Failure executing: GET at: https: at io.fabric8.kubernetes.client.dsl.base.OperationSupport.requestFailure(OperationSupport.java:568)
at io.fabric8.kubernetes.client.dsl.base.OperationSupport.assertResponseCode(OperationSupport.java:505)
at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:471)
at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:430)
at io.fabric8.kubernetes.client.dsl.base.OperationSupport.handleResponse(OperationSupport.java:412)
at io.fabric8.kubernetes.client.dsl.base.BaseOperation.listRequestHelper(BaseOperation.java:151)
at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:621)
at io.fabric8.kubernetes.client.dsl.base.BaseOperation.list(BaseOperation.java:70)
at com.cloudbees.jenkins.plugins.kubernetes_credentials_provider.KubernetesCredentialProvider.startWatchingForSecrets(KubernetesCredentialProvider.java:115)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:104)
at hudson.init.TaskMethodFinder$TaskImpl.run(TaskMethodFinder.java:175)
at org.jvnet.hudson.reactor.Reactor.runTask(Reactor.java:296)
at jenkins.model.Jenkins$5.runTask(Jenkins.java:1131)
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$1.run(ImpersonatingExecutorService.java:59)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
I'm not sure why is it complaining, since executing a curl request to the above endpoint using the jenkin's user token gives a successful result (it simply has no secrets configured in the namespace):
$ curl -k "https: -H "Authorization: Bearer $JENKINS_USER_TOKEN"
{
"kind": "SecretList",
"apiVersion": "v1",
"metadata": {
"selfLink": "/api/v1/namespaces/jenkins/secrets",
"resourceVersion": "63369926"
},
"items": []
}