For Outlook on Mac, on every Outlook startup, my add-in disappears, even though it is visible on OWA. To make the add-ins visible again, i go to managed add-ins in OWA and turn them off and on again. They immediately appear on Outlook, but they disappear again at the next startup. 

This issue started a few weeks ago and works fine on windows. 
Does anyone have any suggestions on how to fix this or why is this happening?