This Knowledgebase article provides information about how to resolve the failure of a plug-in to install immediately after uninstalling the plug-in.
Note: Installation/reinstallation of plug-ins should only be performed on the active server.
Uninstalling a plug-in and immediately reinstalling or installing an upgraded version of the plug-in results in failure of the plug-in to install.
When uninstalling a plug-in, the plug-in must be uninstalled from both the active and passive server. Sufficient time must elapse for Neverfail to complete the uninstall process before an attempt is made to reinstall the same or an upgraded version of the plug-in.
To prevent failure during the installation of the same or an upgraded version of the plug-in, wait until the "Unloaded Plugin" message from both the active and passive server are visible in the Neverfail Application Log. Once both messages are visible, install/reinstall the plug-in.
Neverfail Heartbeat V5.3.0