If you have a new account, they may have assigned a new Primary UserID. 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 Primary, you'll need to log in with the Primary ID. If you need help with that, or if your ID is Primary but you still don't have access, you'll have to contact one of their reps to fix the problem, or perhaps one of the forum reps will respond to your message here.
Hi, Meghanmater! I replied to your Stream Issue post, now I know what caused it and I can help. Please send me a private message with your full name. Thank you!