I have been plagued by this issue for a year or so now, on and off. The nuclear option has always worked for me. You may have already tried it, but I know how painful the issue can be, so I'll tell you exactly what I do in case it helps.
It's tedious, and usually takes 5-10 mins, so I wouldn't call it a "fix" - it's more of a painfully slow workaround; one that should cause Microsoft tremendous shame.
- Uninstall the App
- Open a Powershell Admin prompt, and run these commands: a) get-appxpackage Microsoft.GamingServices | remove-AppxPackage -allusers b) get-appxpackage Microsoft.XboxApp | remove-AppxPackage -allusers
- Restart your computer (not sure if it matters, but I have "Fast Startup" disabled, so if this doesn't work for you the first time, make sure that is disabled and try again).
- Install the Xbox App. It "should" work this time.
PS. Lately, I've had to do this literally every time I want to game - it works the 1st time after I do this, but if I restart/shutdown my computer, it's broken again, and I have to repeat the entire process!