Have you enabled mesh at the "edit venue" setting? Click on the venue, and go to the "edit venue" button on the top right. last choice at the bottom will look like below...
After you complete that process, plug both APs back into ethernet so they get the "mesh" settings pushed to them once. This can take 5mins or so. After that, you can unplug any one of them from wired ethernet backhaul, and mesh will work.