Try this:
Backup your save folder
Move all your files out of the save folder, then start the game
Create a few new saves that correspond with the same save slots that you wished to access before.
Exit the game, then drag your persistent file and save files into the save directory to override. Don’t override the new global file as the old global.RPGMaker file is likely the cause of the issue.
Run the game and your saves should now work.
-RegalBuster