Follow the guidelines below to resolve an issue with the installation of Windows 10 from an ISO image not activating if the system was not previously updated to Windows 10.
Windows 10 upgrade
Most initial installations of Windows 10 are currently from an upgrade from a previous version of Windows though Windows update. However, like other versions of Windows, it can also be installed from an ISO file.
You can double-click on the ISO from within Win 7/8.1 and it will install or boot off the ISO and do a clean install. However, if you are executing a clean install, you will be prompted for a Windows Digital Product Key (DPK).
When you are prompted for a DPK, complete the following steps: