There are a few things that may have caused this problem, and the basic solution is only time will fix it.
If you get a message saying that there is already a session logged in, close all browser windows and wait 15 minutes.
If you get a message saying you have locked yourself out, it’s because you’ve logged in wrong more than three consecutive times. Review your setup letter, keeping in mind that usernames and passwords are case sensitive. Again, wait 15 minutes and try again.
Unfortunately we can not reset or restart your specific control panel under these circumstances.