What causes Outlook add-ins to not load on startup

David Phillips  Yes, it is often because they load slow and this can be caused by something on the computer. The first addin that uses net framework loads it, which can result in it being blamed for being slow. An addin that uses folders in imap or online exchange folders can trigger slow loading too, as Outlook will be slower to load those folders. 

There should be notification in File > Manage COM Addins that says why they were disabled - it should either be due to a crash or because it started slowly.