The add-in is prob intalled but UAC is not allowing it to load. Disable UAC and see if that fixes the issue.
You may also need to grant permissions to the below reg key.
For Outlook Add-In installed as 32Bit Add-In on 32Bit OS or as 64Bit Add-In on 64Bit OS:
For Outlook Add-In installed as 32Bit Add-In on 64Bit OS:
CommVault Messaging Support