Go to your XBox application.
First log out from the app.
Then log in again in the app.
Then try to relaunch your MSFS.
EDIT: I just launched my XBox app to take a look. I get an error message on top of the screen telling that they couldn't log me in. Maybe it's a general MS server issue.
EDIT2: I proceeded to relog in the XBox app and it worked without issues. Not sure what happened, but I could log in without problems, at least
I got the 'insert disc' error yesterday - I just closed the application then booted up MSFS from the Xbox app - I usually use the MSFS2020 executable shortcut - but using the Xbox game launcher instead worked right away
On PC, for the past couple of weeks, MSFS starts in windowed mode every time. The first thing I have to do each time I start the sim is change back to full-screen mode. It's irritating, but livable. I, like you, hope they fix these issues with SU15, whenever that is.
To change from windowed to full screen press ALT + ENTER.
To change from windowed to full screen press ALT + ENTER.
It's been that way since at least FS2002. When I first installed the current sim, I hit that combo out of instinct and was pleased to find that it works.To change from windowed to full screen press ALT + ENTER.