Do you have both the coax and ethernet connected on the Joey? I ask because this morning I was going to (subjectively) compare ethernet to MOCA. I normally have only ethernet plugged into the Joey. I connected the coax (with Ethernet still in) and reset the Joey. Joey could not find the Hopper. Strangely, the Joey showed only MOCA, no ethernet, and the MOCA had the IP address normally assigned to the ethernet. So I disconnected the Ethernet and reset the Joey. Still no Joy. Disconnected the coax, plugged in the ethernet, reset. Buggered.
Long story short, I had to disconnect the power on the Joey, connect either coax or ethernet, but not both. RESET the HOPPER. Reconnect the power on the Joey. Works fine.