So, you've made sure that you've type in your username and password correctly? Make sure of that first. Second of all, try restarting your computer if you haven't already if that doesn't work.
Third of all, this has never happened to me, but I have had problems where it goes black after I log in and such.
Foruth, make sure you downloaded the right version of FeralHeart (this might not be related, but it's worth a shot).
Also, what did you mean by not let you into the game? Did it give you the message, 'Username and Password are incorrect?' I seriously doubt it, but if it gave a ban message, try to think of what you could have done wrong-if you can't think of anything then pm one of the mods.
Hope I could help C: