Maybe I am the only one who has had this issue but it has caused me hours and hours of pain!! So basically when I installed Parallels it downloaded the .iso file for Win 10 and installed fine. The version you have is Home single language unregistered (obviously). So I log in with my digital license account and it will not upgrade windows. After much googling about the issue it is because of the version you automatically install being home and mine being pro. Microsoft offer a 'special license key' which doesn't activate but will change it to the required 'Pro' version however this does not work when you have downloaded and installed it. The fix for it was to delete everything and then start again using the .iso option to instal rather than letting you download it. This enabled me to input the 'special key' and it installed the Pro version by default. I don't know if there is a way you can allow us to choose which version to install but it would have saved me hours of my life! Anyway thought it may help some people if they ever experience the same issue as me.
