I would open a TAC case then so they can look at the details of your setup.config, or you can post your two AP's configs here (via CLI) and someone can look at them to see if something is missing. If the extensed SSID is disabled and the eth0 bridge is setup correctly, the first thing to check is if the mesh is up. If yes but Eth0 won't bridge, then it's likely an eth0 config issue or something with the port/config on the external device.