The symptoms described above most often indicate that the Ethernet port device is being detected, however macOS is not automatically creating a new network service for the device. In most cases manually adding the service by following this procedure can help:
- Click on ‘System Preferences’ (gear icon in the macOS 'Dock').
- Click on the ‘Network’ Application (globe icon).
- In the bottom left-hand corner of the ‘Network’ application, click on the “+” (plus) sign to add a new service.
- Click on the ‘Interface’ drop down and select ‘Thunderbolt Ethernet Slot 1’.
- Leave the ‘Service Name’ populated with the default name and then click the ‘Create’ button.
- Click the ‘Apply’ button in the lower right-hand corner of the application to apply the changes.
- Wait a few moments to see if the Ethernet adapter in the dock starts working.