I had created an Open world in UE5.3 the map was completed and we later moved to UE5.5 during content migration I migrated the map to UE5.5 everything worked fine during migration, after migration completed the map is all blank in UE5.3 as well as in UE5.5. I added the SS for reference any help would be appreciated!
Whilst this may not fix your problem right this second, GIT source control would completely invalidate this as an issue, you can find a few tutorials on setting it up on youtube/google. Sorry I can’t be more helpful.