...I upgraded the problematic system from W10 Home to W10 Pro using the universal Microsoft update activation code. The process was not straightforward...
I tried to do the same upgrade on one of mine. It upgraded easy enough but would not activate. Called MS activation team & tech said it cannot be done. Asked to speak with a supervisor & told him I was looking at the MS How-To-Upgrade web page. Since page has no reference number, could only offer him the url which he did not want, but he did believe me.
3rd one under Show Allhttp://windows.microsoft.com/en-us/windows-10/upgrade-windows-10-proHe checked my Win7Pro PID & said it was valid. Then turned me over to another tech, explained it all again. Let him take remote control of machine & he couldn't get it to activate either. He inputted a new PID & then it worked. Was on the phone with them for over an hour.