I just recently encountered a problem with my Acer Aspire E3-112 notebook keyboard that I had been able to fix and would like to share the solution with anyone who may encounter the same problem.
I had used a USB flash drive to copy some files without any issues. Shortly afterwards, I noticed that the 8 key on the keyboard had stopped responding, but all other keys worked as normal. I had pressed Fn-F11 (NumLk) and the 8 key started working again. Pressing Fn-F11 again disabled the NumLk mode, and the 8 key also stopped working again. I tried rebooting the notebook, shutting down and powering back up, reinstalling keyboard driver, etc, but nothing worked. To rule out Windows OS related settings, I rebooted into BIOS, and noticed that the 8 key still didn't work when I tried to change the time, but the other number keys worked fine.
The solution that finally solved the problem was to shut down the notebook, and then using a paper clip, push it into the Batery reset pinhole on the bottom of the notebook for four seconds. Upon normal powerup, the 8 key started working again.
If your notebook has a removable battery, then removing and reinstalling the battery might have the same effect.