I urgently need help. This is very strange, and It won't let me test the game, it just kicks me back to lobby.

Yes do a log after trying to launch a session,

The editor load log is fairly generic, but I do see your Project Folder is in OneDrive.

OneDrive does not communicate with UEFN very well, so sometimes it decides to restore file changes or deleted objects from the OneDrive cloud without UEFN knowing.
People have noticed deleted objects returning, moved objects relocating, but I would also assume it could affect devices and restore old settings or references.

The first thing to do is either take the Project Files out of OneDrive control or move them to a new location for the project folders maybe C:\Projects.
Use the Preferences in UEFN to add the new location.

After the move, try a Build Landscape and see if anything pops up.

To make sure your using streaming, check the World Settings and see if Streaming Enabled is checked.

Have you Done a Build HLODs yet ?
If so, to test and see if it is a world streaming problem, in the Content browser Add a new World>HLODLayer.
Then go to world settings and change your Default HLOD layer to the new empty one and try to launch.