How To Reboot a Dell Dock

Disconnect the laptop from the dock by removing the USB-C connector from your laptop.
Unplug the power cord from the dock (circular plug that usually has a blue light indicator).
Hold the power button in on the dock for about 30 seconds to drain any residual power.
Open the laptop and reboot it.
After waiting about 30 seconds , plug the power cord back into the back of the docking station.
Reconnect the laptop USB-C connector back into the dock (always do this last)