You might notice that every time you upgrade you need to enable GUI scripting again.
PostLab uses GUI scripting to reset your recent libraries within Final Cut Pro. This is important for several reasons.
The most important one is to prevent you from working on a library that isn’t checked out through PostLab. This way other people might start working on the same library and you end up with sync failures.
macOS is becoming more and more secure and therefor you need to enable GUI scripting with every update. Simply because macOS has detected that the application has changed.
When PostLab opens it will check if GUI scripting is enabled for PostLab. If not you’ll see this screen:
When you click ‘Enable GUI Scripting’ PostLab will launch the correct pane in System Preferences. And you might see something like this:
As you can see PostLab is all ready enabled. This will happen sometimes and is I think a bug in the system. What you’ll need to do is to disable the checkbox for PostLab and then enable it again.