Issue

Changes made to a agent’s configuration are not persisted in its config.xml

Environment

CloudBees Jenkins Enterprise

Resolution

You will need to manually edit the agents’s config.xml file to remove the
temporary offline lines:

<temporaryOfflineCause class="hudson.slaves.OfflineCause$UserCause">
  <description>
    <holder>
      <owner>hudson.slaves.Messages</owner>
    </holder><key>SlaveComputer.DisconnectedBy
    </key>
    <args>
      <string>anonymous</string>
      <string/>
    </args>
  </description>
</temporaryOfflineCause>