If your Thunderbolt 4 Dock (ST-UCT4DM) seems completely dead, with no LED (light emitting diode) indicator and no power reaching your connected devices, start with the power connection. The Thunderbolt 4 Dock is not bus powered, so it will not run on the connection to your computer alone. It needs the included 135W power adapter plugged into the DC (direct current) input port on the back of the dock, which is labeled DC IN 20V. The steps below sort out whether the outlet, the power adapter, or the dock itself is at fault.

How to fix a Thunderbolt 4 Dock that will not power on

1. Check that the included power adapter is firmly seated at both ends, plugged into the wall outlet and pushed all the way into the DC IN 20V port on the back of the dock.
2. Plug the power adapter into a different wall outlet to rule out a dead outlet or a switched off circuit.
3. Disconnect everything else. Unplug your peripherals and the Thunderbolt 4 cable that runs to your computer, so only the power adapter is connected, then look at the LED indicator on the dock.
4. If the LED indicator comes on with only power connected, reconnect the Thunderbolt 4 cable to your computer first, then add your peripherals back one at a time to find the device causing the problem.
5. If you have another compatible power adapter, try it. A replacement supply for the Thunderbolt 4 Dock has to deliver at least 135W at 20V and use a center positive barrel connector measuring 7.4 mm outer diameter and 5.1 mm inner diameter.
6. If the LED indicator still does not come on with only the power adapter connected, and a second compatible adapter makes no difference, the dock or its power adapter is faulty and needs replacing.