I have worked through the suggestions across the numerous instances of white/blank screen in this community, but nothing has worked.
Stepping back — my old Quicken subscription had expired and was renewed this morning. I also had to switch to a different machine because the old one died. So current environment - new Windows 11 (Pro) PC, fresh install of Quicken Classic after subscription renewal. Use of a backed-up version of Quicken Data file ran into the white/blank screen problem. Attempted creating a new Quicken Data file - same problem. Quicken only shows 2 items in the menu bar — File and Help.
To rule out a problem with the new PC, switched to a different Windows machine with an existing Quicken installation. Created a new Quicken Data file - no surprise, but still the same problem. Made sure firewall and antivirus are disabled. Uninstalled (including removal of Quicken folder) and reinstalled a few times. I can access the Quicken site via the Help menu, so validation should not be the issue.
Quicken account shows subscription is active.