delicate rune
Go to installed files > Verify Integrity of the game files.
If that doesn't work, uninstall and reinstall the game.
If that doesn't work, go to betas, install 1.5.1, then go back onto the current version of the game. You'll want to backup your save files before doing so, which is located in AppData > LocalLow > Videocult > Rain World; Just save the Rain World folder.
Basically lets you downpatch the game
Unfortunately not quite sure what other game versions are like, hmmm
Does the game blackscreen as soon as you try opening it? Can you open other campaigns?
Gotcha
It might just be that survivor save in particular- If that's the case, I think you could solve this by going into the backups tab
If that's available anyway
In the options setting ^