If you look at the download section, there are 4 types of downloads.
1 is the real download,
2 is the patch,
3 is for MAC,
and 4 is for FeralHeart+.
If you downloaded FeralHeart+, there are LOTS of errors on that. It also messed up my computer and I had to buy a new one.
If you downloaded the patch, then your FeralHeart cannot work unless you have the original FeralHeart download.
If you have a MAC and you downloaded the normal one, then you must download the MAC version.
If you have a normal computer and you got the MAC one, simply delete it and go for the normal one.
If you did everything right, then your computer must have a virus that doesn't let you play this game.
Your computer is probably old and slow, and considering the great graphics of this game, you can't download any version of FeralHeart on the one you're using.
There's also something called Feralistic, which I doubt you downloaded. It's about as bad as FH+, but it messes up your whole FeralHeart, and you end up having to redownload and lose all the maps you have in your exports. My sister experienced this problem.