Chosen Solution
I had to replace the display on my 2015 MacBook and that went smoothly but as soon as I plugged in the power cord to boot, it seems as if my entire OS was reset because it now only shows me the Choose Language display screen. The problem is that now, my keyboard and trackpad does not work whatsoever. I’m pretty sure the ribbon cable is connected properly to the logic board because the force touch trackpad clicks properly, indicating that its receiving power at least but the keyboard and power button do nothing when interacting with the operating system. I am very desperate for help, because I need my computer working by tomorrow.
Unlike the older MacBook’s and the MacBook Pro’s, you need to de-energize the battery rails before disconnecting the trackpad cable.
Always press this button (Orange) and wait for the LED (Green) on the other side goes out before disconnecting the trackpad cable if you have power applied (best to wedge the power as shown here), otherwise you can kill the MacBook (trackpad has a constant G3H power applied). If that did not help, press this button on the logic board, and plug the USB-C charger. If it is still not working, there is an issue with the logic board and you’ll need to replace it (or better yet just bring it into an Apple Store).
