Can’t access cellular data plan from iPad Pro settings.

I set up AT&T cellular plan for my iPad Pro in March, 2020. I receive monthly payment receipt emails from AT&T. I accessed setup through iPad settings, cellular data. Since then, I’ve accessed the plan through settings>cellular data>Manage AT&T account>view account.

Now, when going through this sequence, I get:

(Shows AT&T logo,) Invalid Access. Please close page and reopen View account. (USMI9991)

View account is only accessed by clicking ‘manage account’ and brings up the same error.

Online myAT&T, their ‘800’ number on my credit card, and my AT&T retail store, were no help. I did find a link to the website to manage my plan, dcp2.att.com, buried at the bottom of the monthly payment acknowledgement email I get from AT&T. I was able to access my account through this link.

After doing some troubleshoot with AT&T (forums.att.com), resetting all settings and updating iPad, AT&T concluded I’m using apple’s embedded SIM (correct, I didn’t place new SIM in iPad) AT&T referred me to apple for the fix.

It seems when I click ‘manage account’ I get View account, and the link to my account is no longer valid.

How can we correct the link settings>cellular data>manage AT&T account>view account to be dcp2.att.com?

Can I remove the account in settings, without cancelling the cellular service with AT&T?