If your PC is NOT downloading the the new update (which is really a freaking whole new UPGRADE) you should stop before you download it yourself from any of the links and check your PC update history. What I learned with one of my PC's and have seen happen to a lot of other folks is that some PC's are missing updates that came out prior to this and that is why it is not installing automatically.
I haven't come across any explanations yet, as to why or what has caused a handful of PC's to miss updates (I thought both of mine were up to date but one was missing about 7 previous updates.)
It will show you which ones you're missing and you can just click 'yes' and it will download and install them (which is how it worked for me) restarting your PC several times...and THEN it will download the latest update/upgrade and install. My PC restarted so many times, I stopped counting. I just let it go until it was done.
I've seen where people have interupted the whole process, thinking it was done, or trying to force install the update when they were 'missing' previous updates.
What's cool (I'm probably repeating myself) is that you can make a USB stick of the upgrade and do it that way, like they did with the original upgrade a year ago, and have it all saved on the usb stick. I don't know how long it will stay good but I imagine as long as you're using a legitimate copy of Windows and all that, it should be good anytime you need it if you have to rreinstall Windows 10.
***The reason I keep calling this new update and 'upgrade' is that the first things I noticed was that my Windows Update files was set back to zero (saying I have not installed any updates, ever) and the whole process created a 'Windows.old' file in This PC>Windows (C:)>Windows.old.
The file is about 30GB in size on my main PC and about 18GB on the other, both dated the day of the update (08/02/2016). So , I assume like the original upgrade, you can use this if you need to go back and reinstall. I plan to hold onto it for at least three to six months, just in case.