yyosha I need more details to understand what you mean when you say
no-joy
Are you saying that you installed the test build of the plugin, restarted Jenkins, and the "Manage Jenkins" -> "System" page was still disabled? If so, then I suspect that you may not be actually running the test build of the plugin. The zip file includes a ".hpi" file. If there is a ".jpi" file of the plugin already in the plugins directory, then that "jpi" file needs to be removed. Jenkins might be loading the released "jpi" file instead of the test build that is in the zip file as an "hpi" file.
Also, in systemctl status Jenkins, I get this right after I install the plugin:
WARNING o.k.s.BytecodeReadingParanamer#lookupParameterNames: Looking up parameter names for public hudson.util.FormValidation org.jenkinsci.plugins.pipelineConfigHistory.model.PipelineConfigHistoryGlobalConfiguration.doCheckMaxHistoryEntries(java.lang.String); update plugin to a version created with a newer harness
That is an expected warning and should be harmless. It should also appear with the current release of the plugin.
The plugin is built with older versions of the Jenkins build tools and allows itself to be run on Jenkins versions as old as 2.346.3. That warning says that the plugin needs to be updated to require a much newer minimum Jenkins version.
I've submitted a pull request to update to a much newer minimum Jenkins version as recommended by "Choosing a Jenkins version to build against". However, I'm not a Cyberark user, so I've not tested either of those pre-release builds with an actual Cyberark instance. I'd love to have you test both of them. If it helps you, I can even combine the two pull requests into a single build so that you can test them together.
Thanks for reporting the issue. I can duplicate the issue. The JavaScript debugging tools report an exception attempting to assign the value true to a field that is part of a null object applyBtn. That is line 192 of the file src/main/resources/org/conjur/jenkins/configuration/GlobalConjurConfiguration/config.jelly in the Conjur credentials plugin source code.
Steps that I used to duplicate the bug: