Chosen Solution
Out of the blue, my laptop’s internal keyboard and trackpad have stopped working. However, I can still use an external mouse and keyboard without issue. Nothing really happened. Opened the laptop one day, and it was unresponsive other than the power button. I have tried all the software resets and have also replaced the battery, since other posts on this website suggested that battery expansion might be an issue. (It was well over 1000 cycles anyways). However, the problem still persists. Posting couple pictures of the internals below. Any help in diagnosing the problem would be greatly appreciated. Thanks!
You need a new trackpad! The flex cable has the keyboard & trackpad input logic which has failed MacBook Pro 15" Retina (Late 2013-Mid 2014) Trackpad make sure you get the one with the cable!
