Upgrade license is digital only, it doesn't come with the actual key. Your Microsoft account itself is the key.
This is the standard alternative method you can try, assuming there's no other underlying issues.
You can go to Settings > System > Activation > Change product key
Disconnect internet, and disable any third party antivirus, key in the generic key instead: VK7JG-NPHTM-C97JM-9MPGT-3V66T
That should get you to Pro. Once restarted, you can connect back to the internet, sign into your Microsoft account. See if it is activated.
If it doesn't, let me know what error you receive, so we can review further if needed.