I would reccomend re-installing the game. Go into your C: Drive or whatever drive you saved it to and into your main Feral Heart folder. Scroll down until you find the un-install button and un-install Feral Heart. Then, delete the Feral Heart folder and the desktop icon if you have one.
Plus, just make sure caps arn't on, num lock isn't on, you're no lagging too much and it double letters, and make sure there are no symbols in your username or password.
Good luck.