The guy who made that video was using a ‘Pro’ version of windows, most ‘Home’ versions won’t have access to hyper-v. What’s more it’s likely something in his specific windows conflict was taking issue with NOX, and performing the steps in the video inadvertently reset whatever was causing the issue.
It’s probably not Intel’s HAXM that fixed the issue, and simply ‘Turning hyper-v ON then OFF again’ almost certainly didn’t fix it, my money is on a bug in his antivirus’ VT-x babysitting module.
TL;DR scour your antivirus software for options relating to ‘VT-x’, ‘VT-d’, ‘Virtualisation’ and/or ‘virtual machines’ and disable any options you may find that reference these.
EDIT: You also haven’t told us what your pc’s specs are. You need a reasonably strong PC to run games on NOX flawlessly. Little netbook with a twin core CPU and integrated GPU probably won’t cut it.