Found an awesome fix at:
https://deploymentramblings.wordpress.com/2014/05/05/keyboard-stops-working-on-windows-8-1-system/
I was working on a client’s system and after I had disabled a few annoying things like the narrator I couldn’t get the keyboard to work anymore. After a search on the internet I found that there was still one setting enabled:
After I switched off “Filter Keys” the keyboard magically started working again. Thanks deploymentramblins!