Outlook VSTO add-in not register in Outlook after run the .exe installer in Office 365

Question

The outlook add-in was built back to Visual Studio 2012/2013 using .net 4. It has been working without any issue on any new machine with Office installation until Office 2016 (professional). The expect behavior is after install the add-in by running the .exe file, when first time launch Outlook, it will load the add-in and prompt to register/install in Outlook.

Recently tested using Office 365(ProPlus) machine seems stopped registering the add-in when launch Outlook. The installation folder is created in C:\Program files\, but add-in is not registered in Outlook->Files->Options->Add-ins. The work around solution is go into the installation folder in C:\Program files\XXXX Add-In\ and execute the vsto file to trigger the registration in Outlook.

I am wondering if this is something expected in Office 365 or anything I need to change/config in the installer? It didn't have any issue in the earlier version of Office/Outlook.

Thanks.

Answer 1

Nothing has been changed so far. First of all, you need to make sure the required windows registry keys were added, see Registry entries for VSTO Add-ins for more information.

If the installer is targeting all users on 64-bit Windows, it is recommended that it includes two registry entries, one under the HKEY_LOCAL_MACHINE\Software\Microsoft and one under the HKEY_LOCAL_MACHINE\Software\WOW6432Node\Microsoft hive. This is because it's possible for users to use either 32-bit or 64-bit versions of Office on the computer.

If the Installer is targeting the current user, it does not need to install to the WOW6432Node because the HKEY_CURRENT_USER\Software path is shared.

For more information please see 32-bit and 64-bit Application Data in the Registry.