Macbook 2017 12" suddenly died after noticing a haptic trackpad issue.

I noticed that my Macbook 2017 12" (i know... it has problems but i love it) had an issue where the haptic touchpad stopped responding. But it turned on perfectly. I fiddled around inside to investigate and in doing so tore the flex cable... maybe it as already torn? Bought a new one and replaced it. And another to make sure it was 100% the right cable for the right year. No improvement. Every other connector looks fine. But the Mac is now dead. No response at all. The tiny battery light is on. The haptic trackpad 'clicks' now but then stops... and only clicks for a while when i unplug and replug in the power cord. I've done all the force restarts and resettings etc. Maybe someone recognises this issue or has some advice before I give up hope. The battery was NORMAL and has a low cycle count and there were no other problems. I did attach the flex cable upside-down at one point while I was looking at ways to fix it- it got very hot - but noticed the error immediately. Maybe this error has done some permanent damage elsewhere. Cheers, Dave