Another option that worked for me (after all day.. downloads considerably slower than Windows Update did) is to download the Media Creation Tool from
https://www.microsoft.com/en-us/software-download/windows10 ... Download the whole thing over again onto a USB drive, and go through the entire install process again.
I booted from the USB, but since I already had Win 10 -kind of- installed it told me to take the USB out, reboot, and run the setup file from the USB from within Windows. So you would just load your USB drive and click the Setup file.
I actually had to download it again TWICE. The first time I chose to just upgrade without downloading it to a USB drive. At 100%, the whole thing just disappeared. I'm sure the files are SOMEWHERE on my computer, but after messing around all day I wasn't going to look for them. So the second time I chose the USB option in the Media Creation Tool.
To be clear, I did not do a fresh install either time. I still have all my files and programs from before the upgrade.
Was long and annoying, but everything is working fine for me now.