please check whether anything is grabbing the MIDI in "raw" mode, might be jackd (-Xraw) or some java application or applet.
as many other linux applications, qtractor uses the ALSA Sequencer (aka. ALSA-MIDI) shared infrastructure, and this becomes pretty much inoperative when some other application takes over any of the old "raw" device interfaces directly or exclusively (eg. /dev/snd/midi*, /dev/snd/seq, etc.)
please check whether anything is grabbing the MIDI in "raw" mode, might be jackd (-Xraw) or some java application or applet.
as many other linux applications, qtractor uses the ALSA Sequencer (aka. ALSA-MIDI) shared infrastructure, and this becomes pretty much inoperative when some other application takes over any of the old "raw" device interfaces directly or exclusively (eg. /dev/snd/midi*, /dev/snd/seq, etc.)
hth.
cheers