Activation server determined specific product key has been blocked?

I got the notification that my upgrade was available from windows 7 Home Prem. I followed the instructions and did a normal upgrade, not a clean install. All my personal files are still on the PC as are my bookmarks etc.

Windows 10 is working fine, but says it's not activated. It shows the last 5 digits of the product key info, and they are different from my previous windows 7 key, so somehow they have automatically changed. My windows 7 key obviously doesn't work to activate 10 either.

I get an error code Error code: 0xC004C003 - The activation server determined the specific product key has been blocked??

At no point in the upgrade did I change or enter any product keys. I just followed the on screen instructions.

What should I do now? I can roll back to 7 but when I upgrade again I assume the same thing will happen?

I rolled back to 7, checked everything was fine it was definitely activated, and all updates installed. I then followed the upgrade procedures again, but am having the same error with trying to activating. This is very frustrating.

At no point during the upgrade did windows ask for a key, and I never entered one.

Thanks for the suggestion. I'll give that a go and report back.

if you have never entered the license key into it then it will be using the manufacturers generic key and this may be the problem.

A problem for MS - because OEM's use a Bios Marker..
Until windows 8 - Dell's would all pull the same activation key for the OS edition

I rolled back to Windows 7, again, so I could enter the product key from the sticker on the bottom of my pc and then try the upgrade. The issue now is I'm not given the option in 7 to enter the product key. The link just is not there in the system page of the control panel. I have two toshiba laptops and neither give me the opportunity to enter it. I have windows 7 on a tablet and it does allow me to enter a key, but on the laptop's that option isn't there?