Found a temporary fix to the Student Finance Unknown Error Message Watch
You have to first login, type your CRN or email and the password. Make sure you confirm your secret answer on the next page. You then have to click the "Login to Account" button and make sure you are redirected to the error message screen.
You simply add an / at the end of the link. If that does not work then add /1 or /?1 and it should work. After that you should be redirected to your Student Finance account welcome screen.
The reason this is a temporary fix is because, after you log out, you will need to re-do the same process. This can only be fixed permanently by Student Finance themselves but I just hope this helped you guys.
I found this out because I thought this error message worked the same way as when Google says, "This webpage has a redirect loop problem." And to fix that was to add a / and then anything after that e.g. /1
If you happen to end up on the error page again then just simply add / at the end of the link each time this occurs.