Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter requires Thunderbolt 3
The Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter requires a host that supports Thunderbolt 3 over USB-C.
If you're having issues with the adapter, or if you were directed to this page when you connected it to your computer, verify that your system supports Thunderbolt 3 over USB-C. Check with your system's manufacturer if you think the message was shown in error. The following Mac computers support Thunderbolt 3 over USB-C:
iMac Pro
iMac models from 2017
MacBook Pro models from 2016 or later
Also be sure to plug the adapter directly into the computer or a Thunderbolt 3 device, not through a USB-C hub. USB-C hubs don't support Thunderbolt 3 connections between their ports.
If you need more help, contact Apple support or schedule a Genius Bar appointment.