"My guess is that your clients are tied to your "old" e-mail sign in."

That's a great guess. The "Intuit ID" process has gotten very cumbersome. You can transfer ownership of one ID to another, now, without needing to contact Intuit to do it for you. You can link them, too. For instance, my Log in has 4 "company names" and Customer numbers linked to my one log in. The QBOA portal would work like your umbrella access, so if you made that fresh, you can use your old log in and "invite" your other ID as "my accountant" or transfer ownership.

And it matters which portal you log into, for what you see. Instead of the QBO portal, you would now be using the QBOA portal. Or, the ProConnect portal.