If this occurs, the first thing to check is to ensure the game/website is not down for scheduled maintenance or due to an unplanned outage. This information can be found on our ProdigyStatus twitter feed here.
If all services appear to be running normally, then this might be due to the inclusion of an unrecognized character in your password.
Examples of characters that have been known to cause issues are:
The @ symbol
The ' (apostrophe)
The - (dash)
To correct for this issue if you do have this or another special character in your password, you'll need to go through the password reset process which is outlined in the article linked here.
If you're still having trouble, please select "Submit a request" at the top of this page or write to us directly at firstname.lastname@example.org