2010 MacPro running 10.13.6 High Sierra.
I see this on the app store, not the normal page -
When I click to restart/install, I get a message "Available updates have changed" / "Click 'show details' to see the available updates. But that does nothing. A restart doesn't install the updates available.
I'm looking for a way to reinstall the App Store App. FWIW, I updated from Yosemite to High Sierra recently and hadn't seen this issue before the update. Mostly all else running fine.
The odd page rendering isn't the real issue, it's the fact that the update(s) offered to me don't install, just the cycle of error messages. Other linked answer has no solution to that problem either.

man softwareupdateThen use it to install updates. – user3439894 Jun 03 '21 at 14:23softwareupdate -i -a– BabyBoy Jun 04 '21 at 08:04