Recently I had to debug a strange issue with an Outlook VSTO plugin where the plugin would install smoothly and load correctly but my custom calendar region was not showing as expected. To complicate matters a little further, I had some clients on 32-bit and some on 64-bit desktop systems so it was not a straightforward install.
You can find the base steps for registering a VSTO add-in here.
Note: An easy check to see if your add-in is automatically loading correctly is to verify that the LoadBehavior key stays at 3. You can keep the registry open while you load your Office application and refresh to see if it was unloaded.
Outlook Form Regions have an extra step though and depending on the desktop architecture you are on, you’ll need to