If everything is completely off, no GPS LED, etc. I would start at the 5V USB connector and work toward the downstream components. If 5V is lost, is there a short that the power supply (wall wart) is shutting down? Or the solder at the connector is suspect?
If you have 5V at L41 (both sides), then check the output pin of the LV33VC regulator (3.3V).
It could be a cold solder joint that finally oxidized or moved and opened up. Good luck and good hunting.
Greg