Chosen Solution
I have macbook retina early 2015. The left part of the trackpad does not work , but the right side does work fine. I tried NVram reset but it dosent help. Sometime the left part of the trackpad also starts to work fine.
You’ll need to replace the trackpad following this guide MacBook Pro 13" Retina Display Early 2015 Trackpad Replacement and here’s the needed part MacBook Pro 13" Retina (Early 2015) Trackpad Somehow you damaged the sensor logic on the left side of the pad (capacitance sensor array). Did you have a liquid spill or crack the glass?
