Sorry for not replying earlier.
When you reformatted your PC, did it affect the drive that had your Blizzard Games installed on it, or just the boot drive?
The issue might be that the boot drive doesn't have the registry keys for where the games are installed. To fix those, you might be able to utilize the Scan/Repair tool in the Battle.net Launcher. If that does not work, you would have to reinstall the game.