Resetting a Dell Thunderbolt dock
Resetting from “bricked”
Dead dock: no power light, no light on the Thunderbolt cable, no response to commands, and no screen, sound, or internet pass through.
How to reset the dock:
Unplug the dock from power and from the computer
Hold the power button on the dock down for 45 seconds
Plug everything back in
Power up.
More Information: Resetting a Dell TB16 Thunderbolt dock (Updated) | Daniel Paul O'Donnell