UE 5 - Failed to Load Map - Message

Hi Everyone, Been using and learning UE4/5 for about a year now moderately successfully, but in the last couple of weeks every new project I start, when I come to reopen it I get a message saying…Failed to load map!..Main.umap appears to be an asset file.

I tried creating loads of new projects, and bring in different assets and saving them, but every time I restart, the same message appears and when the project opens there’s nothing in it, just a black screen. Any one any ideas please as to what is going wrong, I’ve deleted UE4 & 5 and reinstalled them, but still get the same message each time I open a previously saved project. Thank you.2022-03-30T23:00:00Z