Mekkablue Build Symbols Script Not Working?

Hey, any ideas why the Build Symbol Script isn’t working? It keeps saying this…

What version of Glyphs do you have?

3.4.1

Latest of Glyphs 3

Can you try the latest cutting edge version? It should have fixed this. (Preferences > Updates > Show cutting edge versions)

Will do. Can I easily revert to previous version if I need to?

It says please be careful, so just checking I can go back easily

Yes, you can download the regular app version any time form the Glyphs website or download any version from here and have multiple versions installed side-by-side:

It worked. I installed new version - thank you!

Or duplicate the app (rename it to Glyphs 3 Beta) before you update.