I have a c# COM Add-in developed for Outlook that was created years ago in Visual Studio 2010. It was installed on a computer using Office 2010 and works fine. We are now migrating to Office 365. I installed the Add-in and in Outlook's "File".."Options".."Add-ins" it is listed under the "Inactive Application Add-ins". When I click on the Go button under the "Manage" - "COM Add-ins", the add-in is listed but not checked. When I check it, it shows "Load Behavior: Not loaded. A runtime error occurred during the loading of the COM Add-in." The old Add-in was compiled as 32 bit and I tried to install it as that, then recompiled it as a 64 bit app and installed that but it gives me the same message. Should COM Add-ins work in Office/Outlook 365? Is there something that needs to be updated?
1 Answers
Should COM Add-ins work in Office/Outlook 365?
Yes, they should work correctly. There were no breaking changes.
Microsoft Office applications can disable VSTO Add-ins that behave unexpectedly. If an application does not load your VSTO Add-in, the application might have hard disabled or soft disabled your VSTO Add-in.
Hard disabling can occur when a VSTO Add-in causes the application to close unexpectedly. It might also occur on your development computer if you stop the debugger while the Startup event handler in your VSTO Add-in is executing.
Soft disabling can occur when a VSTO Add-in produces an error that does not cause the application to unexpectedly close. For example, an application might soft disable a VSTO Add-in if it throws an unhandled exception while the Startup event handler is executing.
When you re-enable a soft-disabled VSTO Add-in, the application immediately attempts to load the VSTO Add-in. If the problem that initially caused the application to soft disable the VSTO Add-in has not been fixed, the application will soft disable the VSTO Add-in again.
Is there something that needs to be updated?
You need to check add-in prerequisites, make sure that all of them were installed correctly. Then try to log all startup operations and see where an exception is thrown.
If you use VSTO, make sure that you did all the steps described in the Deploy an Office solution by using Windows Installer article.
