You may come across the following message when attempting to access the Imunify360 plugin in the WHM interface:
Imunify agent is not running
First verify the Imunify360 service is up and running. The support link here has guidance on this as well.
If the service is online, then there may be a desynchronization between the agent and the web interface. It can take up to 60 minutes for this to fully synchronize after Imunify360 is installed.
Should the issue persist, then rebuilding the Imunify360 files will be necessary. Stop the Imunify360 service, move aside one of its directories, and then start the service back up:
# service imunify360 stop
# mv -v /var/imunify360/files /var/imunify360/files_backup
# service imunify360 start