As a secondary user, you cannot access restricted areas of My Account
Getting this trying to pay my bill.
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 UserIDs online don't always correspond with name(s) on your billing statement.
If the IDs are not as you expect, contact one of their reps at the phone number on your bill or 1-800-Comcast, or use one of the other options on https://www.xfinity.com/support/contact-us/ and have them fix the problem.