I've had this issue a couple of times no it seems intermittent however, I launch a show with an Ethernet only plugged into Fixturenet and it doesn't seem to transmit to my ART-Net nodes. I've found out that if I change my Hog-Net adaptor settings to 'Obtain IP Address using DHCP' my ART-Net nodes begin to work.
This did not occur on the previous software version we were using 3.0.1, however we did not have Hog-Net IP addresses then.
Hope this makes sense, just finished an overnighter.