As you can login to the website it is likely to be either a typo or a character in your password that the login server cannot accept.
Please use the change password facility on the website (scroll the icons underneath your avatar to the left, click on My Account, then on Change Password). Please change to a password that is only letters and numbers without any spaces or other non-letter or number characters and try that for the game login.
If you still have an issue then please use the Support > Contact Support from the top menu above and submit a support ticket with as much detail as you can offer and we will aim to assist from there.
