Outlook Add-Ins - How to re-enable
If your add-in has disappeared from Outlook, this is more than likely that Outlook has automatically disabled it. Ass Add-ins increase the load time of Outlook it does this if it notices issues with the speed. Add-ins can be re-enabled by following these steps.
Within Outlook select File, scroll down and click on Manage COM Add-ins
On the next screen, click to re-enable the add-in and click Apply (screenshot not available). Close and re-open Outlook and the Add-In should reappear.