When you move, Comcast typically assigns a new account number to your new location, even if it's only a few doors away, and they create a new Primary user ID. They may or may not transfer your previous email address(es) (user IDs/logins) to your new account.
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.
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, options on https://www.xfinity.com/support/contact-us/ don't get this resolved, and an employee doesn't reply to your message here, Comcast Security Assurance should be able to help. You can reach them at 1-888-565-4329 (from https://internetsecurity.xfinity.com/help/report-abuse/). Note that this is NOT one of the general customer service numbers.
The first-line reps there are sometimes not very helpful, so you may need to be persistent and keep at them until you get a satisfactory answer.