The most common fault with the 3P install is the three cables next to the cpu are replaced into the wrong sockets. These cables all have the same plugs and are easily swapped. These connections scan the keyboard & front panel buttons so if both of these are not responding this will be the first place to look.

MH

 

Thanks for the reply!

I contacted the place that's doing the repair and got a bit more info.  He said it powers on, there's no sound when the keys are pressed, and the buttons light up but don't respond/turn off when pressed.  They're getting another jx3p chip from a keyboard to test if it's the kiwi chip that's acting up.