I purchased 10 Pro from from Microsoft Store and attempted to clean install it on a machine that was running Insider Preview. I downloaded the ISO from Microsoft Store to USB using their tool. Installed "Custom". Formatted system partition and nuked my activated Insider Preview. The clean install won't take the key I was emailed by Microsoft. Either by slui or slmgr. After running slmgr.vbs -ato it says key is blocked. It will take generic key during install but won't activate using purchased key. I think I remember something now that you have to upgrade before doing a clean install. What should I try now?