OK, PiAware should back-feed MLAT positions to dump1090 on port 30104. See here:
https://discussions.flightaware.com/ads-b-flight-tracking-f21/piaware-2-1-3-released-t36047.html
Please restart PiAware and check /tmp/piaware.out
It should tell you which port it is trying to connect to for the MLAT output (either 30004 or 30104).
sudo /etc/init.d/piaware restart
I’m not sure why your dump1090 is not listening on either 30004 (the old default) or 30104 (the new default).
Are you using the FA-supplied dump1090 that came with the sd card image? Or did you change to dump1090-mutability?