Hi there,
I’ve just purchased Glyphs 3 recently. The masters icon on my tool bar disappeared so I could not switch between masters. I have checked in Glyphs 2 and it works fine, so it should not be the problem on my file. Please advise. Thank you.
This is an issue with macOS Monterey which is already fixed in the latest cutting edge release. Go to Glyphs → Preferences… → Updates, check Show cutting edge versions and install the lastest version by clicking the Check Now button.