While the game is installed, Right Click > Properties > Updates > Uncheck 'Steam Cloud'
Uninstall the game.
Steam > Settings > Cloud > Uncheck 'Steam Cloud'
Open File Explorer > Navigate to C:\Users\UserName\AppData\Local
Delete the entire folder entitled 'Maine' (if a cache file can't be deleted, that's okay.)
Go to Steam install folder and delete Grounded folder
C:\Program Files (x86)\Steam\steamapps\common normally
Re-install and start the game.