Check your device’s Thunderbolt connection to Mac
If a Thunderbolt device isn’t working properly, it might not be correctly connected to your computer.
Check your Mac: Connect another device to the Thunderbolt port on your Mac. If you can’t use that device, restart your Mac. If you still can’t use a device with the port, your Mac may need to be serviced. See Find out how to service or repair your Mac.
Check chained devices: Disconnect all devices and cables from your Mac, then connect the device directly to your computer using its cable. If the device functions correctly, there may be a problem with one of the other devices. Try reconnecting the other devices and cables to your Mac, one by one. When you find the device causing the problem, review its documentation for further troubleshooting steps.