If I were you, I'd check everything in that section of the board. Look at where the vias go and make sure the appropriate components on the top and bottom all have continuity through the vias with a multimeter. I did this on mine by taking a picture of the top and bottom, and color coded the vias. If the power key on the keyboard doesn't work, there's a decent chance it has something to do with the circuit nearby the CUDA chip (U7).