Found this - resets the thing so the keyboard is recognised as a first time connection :
“You can delete your user preferences and see if this will solve your problem.
Before deleting user preferences, note any specific preference settings that you’ve made, and save any custom key commands you've created. Deleting preferences removes any custom preference settings and custom key commands.
To delete the user preferences, do the following:
Quit Logic Pro X.
In the Finder, choose Go > Go to Folder.
Enter ~/Library/Preferences, then click Go.
Remove the "com.apple.logic10.plist" file from the Preferences folder.
If you upgraded from an earlier version of Logic Pro, also remove the "com.apple.logic.pro" file.
Restart your Mac.
After deleting preferences, open your project and try to reproduce the issue that you were experiencing. If the issue no longer occurs, open Logic Pro X preferences, reapply your custom settings, and import your custom key commands.”https://discussions.apple.com/thread/250438384
I think this is reasonably common knowledge amongst the enlightened, I’ve seen people posting about preferences folders before. I hope this helps someone else though.