I use Ardour 6.9 with jackd.
I created two MIDI tracks with Calf Fluidsynth and LSP-Multisample x12 stereo. I can get any sound with the virtual keyboard or the keyboard used to test the patches that can be selected for my track.
The only difference is that with the LSP-Multisample x12 Stereo, I can see some activities in the volume meter of my track when I use the virtual keyboard.
Audio tracks are working well, I can hear and register my guitar in them.
How can I fix it?