It appears as if the Windows Game Bar is causing issues with using your mouse to click on items in WoW. It would be nice to be able to use the Game Bar, it has some nice functionality like volume controls, pc monitoring, and Spotify control.
With no addons installed:
1- Enable Windows 10 Game Bar
2 - Log in
3 - Open Bags, click an item, it works.
4 - Win-Z to show the Game Bar overlay, close the overlay
5 - Try and click items again, it doesn’t work. Relogging does work though.