Same issue here. I haven't played in 3-4 months. Game updates and then I notice this issue.
Upon further use, I notice two things happening. I have to shut down my computer completely (not restart), then start my computer, then launch MSFS2020 to see my game settings (2560 x 1440 display, DX 11, TAA, etc).
But if I just re-start my computer, after force-closing MSFS2020 via Task Manager, FlightSim will default to what appears as the "factory settings"(?) that default to DX12, 3840 x 2160, etc.
Guess I'll come back in another few months to wait on Asobo for a fix.
Incidentally, I still don't like 2024. I'm a low-altitude night flyer and the night lights in 2024 do not look real, are too bright, too white, and Saint Paul's Cathedral is washed out in super-bright lights.