Here is my opinion.
I deleted my profile from “everywhere” from MSFS24 (under manage).
Restarted and the game launched.
Once in the game, I picked a A320 Brocard I think, and tried set up a flight.
When I clicked “Fly now” it just sat there for 20 mins.
I rebooted and then got the 98% loading screen again.
I am guessing it was try to load that plane.
Deleted my profile again, and the game launched with a default aircraft of course.
Seems maybe some of the planes we used in 2020 are not compatible.
Hope it helps someone out there.