It frequently happened to me that some buttons stop functioning on Dell laptop such as Enter and Back button. The reason that this happened to me was pretty simple, my laptop gets hot fast. Some buttons stop working at high temperature and I’m not sure about the technical facts behind it.
Whenever this happens to me, I turn off my laptop and leave it for some time to cool down. And then the whole buttons on the keyboard start working again!
Please make sure to prevent your laptop from getting hot. It might burn your memory or CPU.