Have you tried in an incognito (chrome) or private window (firefox, IE)? Usually when I get a 400 error on the GoDaddy site, it's due to caching in the browser itself. Give that a shot and see if you can access it that way.
If not, your only resolution would be to contact phone support or live chat. (Link at top of page.)
I am a GoDaddy End User - Just Like You * Please note that I offer free advice on this forum. I DO NOT answer private messages. Please ask your question in the proper forum so the answer can assist EVERYONE in the community and not just you. Thanks! *
Once your issue is resolved, please be sure to come back and click accept for the solution