ISO download from Microsoft directly. Use Rufus to make an installer USB. Click the "I do not have a license key" option. Who cares about the watermark.
HWID is permanent, even after Microsoft fixed the method that massgravel was using. It only affected new installs because people couldn't run the script to activate Windows permanently.
Hm, I could have sworn I had read an article around here (roughly the last two months maybe, likely more recently) saying that the MAS had been patched by Microsoft, but now I can't find anything about it at all. Odd.
They patched new HWID requests being sent, but any existing licenses made with those methods are fine. That was only one of several ways to spoof yourself legitimate, though. The rest still work.
I'd start there and see if it can be used for 11 or upgraded through the versions. Then I'd take a "clean" backup and use that to re-install in the future, instead of a new ISO.