So doing a show on a Compact XT running 220.127.116.11 with Art-Net output configured on Con1 with a single broadcast configuration, MA net was not in use but I configured it on con3 just incase. Everything works as you would expect, until I physically shutdown and the desk and turn it back on (Reboot did not seem to cause the issue). After I turn the desk back on Art-Net is not transmitted even though the Art-Net dialog Enable Output is On. To get Art-Net back on I had to tinker a little (not exactly sure what got it working again though).
I found if I moved the Artnet Interface to con2 or con3 it worked every time after a reboot or power cycle.
I never noticed this on my Light but i suspect I never used con1 for Art-Net.