This sounds like the "Spinning Castle problem":
In order to get out of the Spinning Castle problem, you need to open a private(Firefox) or incognito (Chrome) window , go to dominion.games, enter your Name and Password, but don't click "Login". Instead, click on "Kick and Resign" (rightmost button below the login area). Then you should be able to login normally (no need for private/incognito tab).