Chosen Solution
So there’s a ton of questions and answers on here, many coming down to possible issue with ribbon cable for track pad, or update to newer version of OSX, etc. Basically, on a friend’s 15-month old MacBook Pro, trackpad just stops working (no haptic response when using it, no movement no pointer, etc). I did a clean wipe/install/updated her to High Sierra, and after about 8 hours, it finally reoccured after laptop was closed. Weirdly, then I plugged in a USB mouse, and 30 seconds later … trackpad was responsive again – and at the same time the computer brought up the mini pop up saying keyboard wasn’t recognized, even though i did not attach an external keyboard. Does this particular behavior indicate anything to all the smart people who know this stuff much better than I do? One quick addition: If this is a loose cable, it’s pretty amazing that it worked all day and then stopped and then, without computer moving a hair, started working again.
Your systems design has the trackpad cable riding on top of the battery. If you review this IFIXIT guide: MacBook Pro 13" Retina Display Early 2015 Trackpad Replacement Jump down to Step 7 to pull the cover plate, then jump down to Step 17 which walks you through the removal of the ribbon cable. I would start there MacBook Pro 13" Retina Touchpad Flex Cable, Early 2015 A common issue is liquid damage. This could even be someone using a spray cleaner onto the uppercase which seeped into the trackpad and/or keyboard. I always recommend spraying the cloth then wiping the case with the dampened cloth. As your keyboard is also fritzi, this could be a swelling battery which is pressing on the cables. A good inspection should tell you if its blistered up. I would run coconutBattery to check the batteries health. Let us know what you find
