Unable to make account changes, and retention can't access my account either

We've been Xfinity customers since 2015 and have Diamond status, with residential internet and TV, six Xfinity Mobile lines, and a separate Comcast Business account at our business.

For about a week I've been unable to make any changes to my account because of this error:

"Looks like we can't process your request right now. We need to verify your contact information to keep your account secure. Make sure to update your phone number and email address."

The phone number and email address on the account are already correct. The error tells me to update my contact information, but it also blocks me from doing exactly that. I also can't enable two factor authentication or make other account changes. It happens across multiple devices and browsers; this is an account-level issue on Xfinity's side.

I've spent hours on calls and chats, visited an Xfinity store, and spoken with retention, supervisors, and Advanced Resolution. Nobody has been able to fix it. When we called retention, they couldn't even access my account information. Xfinity's own reps are locked out too.

The Advanced Resolution call ran three to four hours and covered pricing as well, since our discounts are ending soon and our bill is about to go up substantially. The representative offered significantly better pricing and said she wanted to keep us, but she declined to open a support ticket for either issue, and the offer was never documented on my account. I have no case number and no record of any of it. I asked chat support afterward for the notes from that call and was told they can't provide notes from an Advanced Resolution call.

She scheduled a callback for Friday, July 24 between 4 and 5 PM and confirmed she had two phone numbers she would try. She never called either one.

We also have a written quote from another provider covering device upgrades on all six lines and internet at both locations for less than we pay now.

Can someone please review my account, clear the hold on it, and tell me what loyalty options are actually available?