Error occurred with installed audio unit plugin

Greetings rs09, 

We have an article that goes over some steps for when Garage Band isn’t working on your Mac. If GarageBand isn't working on your Mac We’re including a summary of the steps below, though each is broken down in much more detail in the article - 

Try these steps in order

After trying each step below, test GarageBand again to see if you've fixed your issue. 

1. Restart your Mac
2. Update GarageBand
3. Check device or software compatibility
4. Use built-in audio with GarageBand
5. Open GarageBand without audio input and output
6. Disable Audio Units plug-ins
7. Test with a new project
8. Test GarageBand with a new user account
9. Reset GarageBand preferences

Thanks. 

Hey there rs09,

From the article we previously linked, here's how to disable Audio Unit plug-ins:

If GarageBand isn't working on your Mac - Apple Support

Disable Audio Units plug-ins

If you're using Audio Units plug-ins, try disabling them. Damaged or incompatible Audio Units plug-ins can create unexpected behavior in GarageBand.

To disable Audio Units plug-ins:

1. Open a project in GarageBand.

2. Go to GarageBand > Preferences > Audio/MIDI, and deselect Audio Units. 

3. Play back a project that has been experiencing issues. 

If the project opens and plays back properly, a plug-in you're using in the project might be damaged or incompatible with your version of GarageBand. Check with the manufacturer of the plug-in for support. 

Regards.