It’s installed, but isn’t open. Let me give it a try and see.
Edit: It’s already disabled in Xbox app, so it’s not that either. 
Edit 2: Also, the launcher opens perfectly fine… it just doesn’t log in. It’s like there’s an issue connecting to the login servers themselves.
Edit 3: After a little fiddling with the launcher settings, I managed to get in to the actual launcher (without logging in) then logged in while looking at the game list/news/etc.
Open the Launcher
Click the cog above the login fields (top right)
Click ‘continue without logging in’ - The launcher should hopefully load up with your games etc.
Click to ‘go online’ (top right) and try logging in there.
It failed once for me, then worked the second time so… might just need a bit of an internal kick? shrug