2011 MacBook Pro High Mac OS X Sierra, has performed all security and system updates.
One morning (no rollover or fall), my touchpad did not answer, the keys were generally insensitive, I hit them five times and maybe a letter to type. A few minutes later, nothing worked anymore.
The external keyboard and mouse work.
Tried smc, PRAM, tried to switch to safe mode, tried to reboot via disk mode, safe modes, replaced the trackpad, performed a thorough hardware test without claiming any hardware problem, cleaned the inside of the laptop.
Areas of concern:
When I go into system preferences -> trackpad, it means that no trackpad has been found.
Hardware test in Internet recovery mode: no error (d control)
(D at startup) The hardware test said initializationfailed: unable to run the diagnostics. The DEC500 is trying to run applediagnostics again. If the problem persists, contact Apple Support.
So, I do not really know what to do and I did not know if there were other options I could use to fix the software so that it works again.
Thanks for all the suggestions and a super thanks to anyone who can find a solution to this pain of a problem.