Are you trying to log in from a school/public internet?
Schools usually have UDP internet protocol blocked to avoid any online games to connect.
If you are using a router, try to conect the computer directly to the main internet cable.
Routers can have some bad firewall settings.
Can you play any other online games? (non browser games, like world of warcraft, age of empires, etc.)
If other games using UDP protocol works fine, then the problem is just with FeralHeart.