[SOLVED] Troubleshooting the "Display Layout Changes" trigger

[UPDATE] The macro was in a "Palette" Group so it was never activated. It works well if it's in a normal group.

I'm trying to play with Sal Soghoian's Assistive Keyboard trick, using an iPad as a secondary touch keyboard. (see :Automators 36: Sal Soghoian's Control Panel)
I'm using Duet to run the iPad as a screen (not forking 80 bucks + VAT for a Luna display just yet) and it's working well.
BUT, it seems I can't get the Display Layout Changes trigger to work (I want to use it to open the assistive keyboard when the iPad is connected, and turn it off when it's not)

Here's a test script using the trigger. I can run it manually, but plugging/unplugging my external 27inch monitor (HDMI) or running/quitting Duet on the iPad, which CLEARLY results in a Display Layout Change, does NOT trigger the macro.

Has anyone else faced this issue?

Test Display Issues.kmmacros (1.7 KB)

Answering my own question so others don't need to look as stupid as I do: the macro was in a Palette Group, so it was never going to be triggered. .....
Oh well - we live and learn.