Chosen Solution
After successfully replacing the battery, which I ordered it from iFIXIT, the keyboard and trackpad stopped working. I followed the guide steps exactly and was very careful using the adhesive remover liquid not to drip over the trackpad. Anyone else has had the same issue? Any solution? Thanks!
The keyboard and trackpad in this series uses a single cable from the trackpad to the logic board to send the signals to both. You either damaged it or the battery did it for you ;-{ Follow the guide again MacBook Pro 15" Retina Display Mid 2015 Battery Replacement Stop after Step 5, Jump down to Step 27, You’ll need to replace the MacBook Pro 15" Retina (Mid 2015) Trackpad Cable Presently iFixit is out of stock here’s the Apple P/N for the part 821-2652. Also inspect the logic board & trackpad connector’s for damaged pins. You also want to be careful not to over do the needed bends a soft fold is all thats needed. And lastly, make sure there is slack on both sides of the battery as well
