Unfortunately there a starting problems with MSFS2020 too.
These problems occured shortly after the release of MSFS 2024.
See topc " MSFS 2020 is now not accessible (30 November 2024)":
After nearly two days without problems these starting problems are back again today (17:00 UTC 2024-12-01)
I would like to play MSFS2020 like before.
If you cannot solve these problems then don’t expect that I will buy MSFS2024 !!