Headphones silent w PianoTeq but work with other sources

I have an old and new MacBook Pro retina. Had PianoTeq on the old one for a while. Just installed PianoTeq on the new one. Headphones plugged into the output socket on the old one work. On the new one, PianoTeq ignores the headphones and the sound still comes out of the laptop speakers. If I switch to playing from the Apple Music App the sound starts coming out of the headphones. Switch back and it reverts to the internal speakers. So the headphones are fine and the plug and socket are fine. Must be something in the App?

The older laptop is running PianoTeq 7.5.4 20220331 / Mac OSX 10.15.7
The new l laptop is running PianoTeq 7.5.4 20220331 / Mac OSX 12.6.3

I can't find any PianoTeq, or Mac setting that would account for why the older one works and not the newer one. Perhaps PianoTeq has a bug on the newer Mac OS.

I did notice that the velocity curve is crucial to getting decent balanced volume.

Incidentally, I noticed in the past that I can use Bluetooth output for Apple Music, but PianoTeq ignored it. I'm wondering if there are multiple pathways that sound can be routed from the DAC to the output destination and that the output choice is ignored on one route and sent directly to internal speakers. Could the app software not be recognizing some output settings.

A restart made no difference.
Any help appreciated. Thanks.