Ah, sorry. XD
Open up the game. On the login screen, click "options".
Go to "video" and change the "rendering subsystem" to the option that it's not currently set to, as there are only two of them. (Keep in mind, if this makes your game look weird, change it back right away.)
If that doesn't work, open up your FeralHeart folder, which will be in Computer>Local Disk. Scroll down and double click "unins000" to uninstall. After doing that, delete the FH folder completely and then re-download and reinstall. **MAKE SURE to back up any maps/custom files that you have BEFORE uninstalling**
Best of luck~