Can't activate Windows 10 after upgrade from activated 8.1

hello, i just upgraded my original Windows 8.1 to Windows 10, and when i try to activate it, Windows gives me an error


"Windows cannot be activated, please try again later"

How can i solve this?

I have the same issue. Upgraded from a fulyl legal and activated Windows 8.1, but Windows 10 tells me, that it can not be activated and I should try again later. What exactly is wrong here?

Is there an error code?
By the way, my license key ends with "3V66T" too. What's the first character of your license key? Now I'm wondering if all the people who have license problems have the same license code.

Is there an error code?
By the way, my license key ends with "3V66T" too. What's the first character of your license key? Now I'm wondering if all the people who have license problems have the same license code.

Mine starts with V and ends in 3V66T and my copy is Activated. And to add to the mix, I didn't Upgrade but clean Installed.

@mrplt
Why "too"? But it's true, mine ends with the "3V66T" as well. How did you know? If I click the "Error details" link I only get an empty box with an empty input box, looks like a bug to me.

@mrplt
Why "too"? But it's true, mine ends with the "3V66T" as well. How did you know? If I click the "Error details" link I only get an empty box with an empty input box, looks like a bug to me.

I wrote "too" because according to the screenshot fjk61011 has posted, his/her product key also ends with 3V66T.

I have AIDA64 installed, that's how I found my product key.

I have the same issue, upgraded via the Media Creation Tool, from Windows 8.1 Pro to Windows 10 Pro, everything went smoothly, then this. Same product key that ends in "3V66T" Kinda odd!

If I don't get through to someone soon on the phone with Windows Activation, I will revert changes back to Windows 8.1.

same product key end with "3V66T" too, it is a generic key, since windows 10 activation is based on hardware id.

same product key end with "3V66T" too, it is a generic key, since windows 10 activation is based on hardware id.

I see, I didn't know that.

Can I reinstall Windows 10 on my computer after upgrading with free upgrade?

Once you’ve upgraded to Windows 10 using the free upgrade offer or Media Creation Toolon an activated Windows 7 or 8.1 PC, you will be able to reinstall, including a clean install, on the same device. You won’t need a product key for re-activations on the same hardware. If you make a meaningful change to your hardware, you may need to contact customer support to help with activation. You’ll also be able to create your own installation media like a USB drive or DVD, and use that to upgrade your device or reinstall after you’ve upgraded.