Did you have to remove the head for the trip upstairs? If yes, check the 2 inline connectors near the bottom of the head. Do the wire colors match up on either side of those two connectors?
Plugged up, power switch on? Outlet verified power?
Start in the lower cabinet. All cabling to/from the transformer that has connectors, squeeze them together with GI Joe Kung Fu Grip.
Up in the head, on the power supply board reseat the square connectors near the bottom of the board.