Can't hear audio on Linux

Hi

Novice here.

I created a new session and added a MIDI track. I can see that when I press my MIDI keyboard’s (AKAI MPK Mini 3), the volume (?) bars move however I can’t hear any audio:

Any ideas what could I be missing?


Edit: just noticed these 2 errors:

2021-02-17T00:24:56 [INFO]: AlsaAudioBackend: adjusted output channel count to match device.
2021-02-17T00:24:56 [WARNING]: AlsaMidiIO: Cannot acquire realtime permissions.
2021-02-17T00:24:56 [WARNING]: AlsaMidiIO: Cannot acquire realtime permissions.
2021-02-17T00:24:56 [WARNING]: AlsaAudioBackend: cannot acquire realtime permissions.
2021-02-17T00:24:56 [ERROR]: Failed to create slave device 'hw:Audio,0' error -2

2021-02-17T00:24:57 [ERROR]: ALSA failed to add 'hw:Audio,0' as slave
2021-02-17T00:24:57 [WARNING]: Video-monitor 'xjadeo' was not found. Please install http://xjadeo.sf.net/ (a custom path to xjadeo can be specified by setting the XJREMOTE environment variable. It should point to an application compatible with xjadeo's remote-control interface 'xjremote').

see also http://manual.ardour.org/video-timeline/setup/
2021-02-17T00:24:57 [INFO]: Loading menus from /app/etc/ardour6/ardour.menus
2021-02-17T00:25:12 [WARNING]: Falling back to Reasonable Synth for Midi Audition
2021-02-17T00:25:12 [INFO]: Loading plugin order file /home/nocturnal/.var/app/org.ardour.Ardour/config/ardour6/plugin_metadata/plugin_order
2021-02-17T00:25:12 [INFO]: Loading history from /home/nocturnal/Untitled-2021-02-17-00-24-49/Untitled-2021-02-17-00-24-49.history
2021-02-17T00:25:12 [INFO]: Untitled-2021-02-17-00-24-49: no history file "/home/nocturnal/Untitled-2021-02-17-00-24-49/Untitled-2021-02-17-00-24-49.history" for this session.