I just tested it in the latest version of Firefox, and it works fine for me.
Have you tried using different browsers? Do they all produce the same result? Also, could you perhaps show a screenshot of what happens?
I do know that before they did have issues with the sign up on the game, which prevented any new player from joining. But I do know they fixed it as well. So I am unsure if your problem is related to that.
If you try with different browsers and you still have the same result, you may want to see if any of your friends can get it to work. If they can, then you may be in luck. If not, then you may need to contact CCR and see if they can help you out.