some things to check:
Enshure the sound is not muted with
alsamixer
or
alsamixer -c [card-number (find out which with: aplay -l )]
(TAB more options, ESC quit, M un/mute)
what's the output of:
lsmod | egrep "^snd_usb|^snd_pcm|^soundcore"
have you selected the right output in qjackctl