Cannot login after upgrading from 2016 to 2020 version

I have been using Quicken for decades, and finally upgraded to the latest 1-yr subscription. When I open Quicken now, I get a brief glimpse of what I expect to see, then that is replaced by a screen asking me to sign in. So I sign in. Then I get a screen that says: "Did you purchase Quicken from Quicken.com? If you're seeing this screen it's possible your Quicken subscription is linked to another Quicken ID. Please choose sign out and sign in again with the email address associated with your Quicken purchase."

There is no other email address that I have used, and I have the confirmation email from today's upgrade proving that I used the same email address. And, when I log into My Account at quicken.com, all I can see is my 2016 purchase, not today's purchase. It would seem that somehow my new purchase has not "merged" with my previously-existing account.

As of now, I cannot use Quicken at all and cannot get past this login screen.

Has any one else had this happen, and if so, how did you fix it? Thanks for any help you can provide!