Zynaddsubfx, midi, no output

Hi there,
lately I am experiencing issues with my Midi-Keyboard, Zynaddsubfx (Zynfusion, lv2) and Ardour 5.12 on Linux.
First of all everything is working fine e.g. with SimpleSynth, so I dont think there is an issue with the basic setup.
When I press Keys on the Keyboard the Keys on Zynfusion’s builtin Keyboard light up so it is definitively receiving signals. However no output is generated, also indicated by Ardours volume bars. Pressing virtual keys in Zynfusion generates tones. In this case the mod-wheel is working as well . Swapping out Zynaddsubfx with e.g. SimpleSynth without changing any other settings works as expected.

Where could I be looking for a misconfiguration?

Thank you in advance

I’ve seen unlicensed version of zyn-fusion behave that way. The synth remains silent except when using the plugin’s own GUI, where the note-event is started but attack is cut short. Could that be the issue?

Thank you for your reply.
Unfortunately I was unable to get any further.
I am using the current kxstudio version (zynaddsubfx-git) and it was working at some point although I can’t confirm the exact version and configuration from back then.

Does it work in other LV2 hosts? maybe try in jalv (after starting jackd):

jalv.gtk http://zynaddsubfx.sourceforge.net

or perhaps qtractor or since you’re on kxstudio, in Carla.

I’m currently quite a bit busy so I don’t have much time for in depth debugging. So far I couldn’t get it to work in standalone or carla standalone, however it is working in an lmms project via carla.
Furthermore I still have no clue where that problem could be coming from since I am pretty sure I didn’t change the configuration and software versions since it last worked.

I finally had my facepalm moment!
The respective channel was muted in Zynfusion’s internal mixer.
The wrong channel was selected in part settings.