Case : Upgrading Windows 10 Home to Windows 10 Pro on an HP Pavilion Laptop with an OEM License bought from a retailer, you get an error message while trying to upgrade with your new Windows 10 Pro license key.
Use first the default Windows 10 Pro Key :
VK7JG-NPHTM-C97JM-9MPGT-3V66TThis should make the upgrade to the Pro Version, if you have issues, try to put your PC in offline mode.
Reboot !
Now you can activate your Windows 10 Pro with your legit OEM license Key :
Start > Settings > Update & Security > Activation and enter your Key.
On kinda the same topic, a really useful tool to get different version, language etc of Windows ISO :
https://www.heidoc.net/joomla/technology-science/microsoft/67-microsoft-windows-iso-download-tool
