Hi All!
I found a possible reason of the issue.
If its not your user profile name of Windows, check that:
Make sure that the account that you used to play MSFS2020 or to play other game (you main account) is a local admin account.
If you have, like me, a seconde account who are admin, to keep a certain security on your main account, you need to change, on your admin account, the type of account of your main account (change as an admin account). then, go back to your main account, run the installer, and then, when they reauest to put an admin account, click "more choice" and select the name of your main accont (and just put the password)