I have a shiny new MacBook Pro (13-inch, 2016, Four Thunderbolt 3 Ports) running Sierra (10.12.4). When connected to my Apple Thunderbolt Display via an Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter, the ethernet is not initially seen. If I delete "Display Ethernet" in network settings and reconnect the display, then it rediscovers the connection and starts working OK.
But, when I plug into another identical display (I have one at home, one in the office) I have to repeat the process. This is a real PITA as I move between home and office every day.
Any ideas? My previous Macbook Air connected seamlessly with the ethernet of either display.