What profile are you asking about exactly?
They may have assigned a new Primary UserID and account number and neglected to transfer the IDs from your previous address. Double check your UserIDs on your home system with the Lookup tool at https://idm.xfinity.com/myaccount/lookup. After you enter the requested information you'll see a list of the UserIDs on your account and an indication of which one is Primary. Be aware that the Primary UserID online doesn't always correspond with a name on your billing statement.
If the ID you are using is not listed, you'll need to log in with the Primary ID. If you need help with that, need to have your existing IDs transferred, or if your ID is Primary but you still don't have access, contact one of their reps at the phone number on your bill or 1-800-Comcast, or chat with them at https://support.xfinity.com/chat and have them fix the problem.