Could the circuit board be bad? If a button still won't work, test the corresponding circuit board contact pad. Touch a small piece of conducting foil to the circuit board pad.

If the circuit board contact pad is clean but you can't get the button to fire, there might be a problem with the electronics on the circuit board. That repair is outside the scope of this guide.

If a piece of foil triggers the button, then there are 3 possible repairs. 1) Apply more conducting paint to the bottom of the membrane, beneath the non-functioning key; 2) Purchase tiny round conducting dots to glue to replace the failed conducting paint; or 3) Glue a piece of conducting foil over the failed conducting paint.

Reapplying conducting paint is the "right" way to fix this, but the paint costs a lot: $10-$30. A set of round conducting dots might cost $10-$20. Therefore, I favor cutting out my own circle of conducting foil.

Thin adhesive-backed metal foil is readily available from electronics suppliers. I had some on hand so I cut out a round piece and stuck it to the bottom of the keyboard membrane for the failed Power key.