Keyboard and trackpad not working

I changed my battery carefully, and after that Keyboard and trackpad stopped working.

This seems to be a common problem and I have spent a lot of time going through all proposed solutions without success.

I did all the boot resets suggested. I bought a replacement flex cable, which didn’t do anything. I then bought a replacement trackpad thinking that was the problem, again with no success.

At this point I am thinking maybe I screwed up the motherboard. I have not replaced the keyboard as I assumed since the new trackpad didn’t work the issue is not the keyboard.

Any suggestions? Computer works fine with bluetooth keyboard and trackpad, but not the built-in ones.

Thank you