Chosen Solution
Keyboard not Working (Power Button works, trackpad works), replaced the keyboard but still the same issue. I have mid-2015 Macbook Pro Retina, the keyboard suddenly stopped working. I noticed the power button still worked. SMC can’t be performed. What has been tried so far: Replaced the inbuilt keyboard completely - same issueReplaced the trackpad cable - same issuetested with a wireless keyboard - wireless keyboard works without problemsReplaced the battery - no changeDisassembled and reassembled everything - no change I have no idea what to do next, is it a hardware issue or a software issue at this point ? Should i just give up
So the power key on this model doesn’t really interface much with the rest of the keyboard circuitry so as long as the keyboard connector is getting that signal it basically goes straight to the SMC. Which is probably why that still works. Trackpad also has very little to do with keyboard on this model (which is not the case for many newer ones) But I would have told you to replace it anyways, they are notoriously crummy on this model. But being that you have replaced the keyboard itself and the trackpad cable, I am beginning to think this might be a board level issue. Have you had a look at the back side of the logic board? If you have a multimeter I would start taking diode mode measurements of the keyboard connector.
