I’ve tried using the plugin manager and manually importing the Red Arrow plugin without any luck. I continue to get errors and warnings of why it isn’t working…
I have installed the ‘cutting edge’ version and it too doesn’t solve the issue.
I have this problem on my work and my personal machine, both are running Sequoia 15.3.1
I’m running other plugins from the manager that work perfectly!
The plugins that work for you are written in C/ObjC and do not require the Python module. Red Arrows requires the Python module, which apparently did not install properly on your machine.
More precisely, the repository got corrupted, which causes the HEAD error message.
So, go to Script > Open Scripts Folder, navigate to the Repositories folder and delete the folder called ‘GlyphsPythonPlugin’. Leave the Repositories folder open.
In Glyphs, open Window > Plugin Manager > Modules and reinstall the Python module. While you are waiting for it to install, switch back to Finder and watch the Repositories folder. You should see ‘GlyphsPythonPlugin’ reappear, look inside, and once it starts filling up with stuff, particularly a subfolder called ‘Python.framework’, switch back to Glyphs.
Restart Glyphs.
After Glyphs restarted, see Glyphs > Settings > Addons > Python Version. It should read ‘3.11.9 (Glyphs)’, perhaps you have slightly different numbers. If the popup is empty or reads ‘Python.org’, you need to switch to the Python version that says ‘Glyphs’, and restart the app again.
If it still does not load, and you get new error messages saying that some plug-ins could not load, go to Glyphs > Settings > Updates and turn on both Debug Mode and Cutting Edge Versions, update the app and confirm once it prompts you to restart again.