Unable to install Apps from the Mac App Store, popup with no buttons except cancel

Mac Studio M4 Max

Sequoia 15.7.3 (latest Sequoia as of December 2025)

Third-party keyboard, no Touch ID.

Any app on Mac App Store, click Get, click Install, then the popup only has a Cancel button. There is no confirm or whatever it's supposed to say.

I've seen this asked before, and most said it eventually went away on its own with no solution.

I've tried signing out the Mac App Store, back in, updating to 15.7.3, rebooting...

Any ideas out there?