A friend has a MacBook Pro, 2013 version. She’s been running 10.9 (Mavericks). Last night she tried to update the system to High Sierra, with every outward sign of success.
The App Store Updates page now says that High Sierra is installed. The problem is that it’s not: her Mac is running Mavericks. I’ve tried restarting and restarting from the recovery volume but it stays as Mavericks and the App Store continues to maintain that High Sierra is installed.
I’m stumped. Any help gratefully received.