Cannot Activate - no errors given

If pc came with 8.1 preinstalled, key will be in bios.

Try running showkeyplus to see if it picks up original key.

If you do not get a result, you should call MS and explain it has previously activated, and they should be able to check your hardware id info with the activation servers for a match. Make sure you are talking to somebody who knows what you are talking about. The quality of some MS staff is decidely questionable.

pakZ said:

Hey cerberus,

thanks for your reply.

Showkey helped me to retrieve the Key that is being used and upon entering/updating it manually, I now have gotten at least an error message.
Sadly, it is 0x80004005, which apparently means that it is an unknown error (which is somehow equally hillarious as the "unexpected error"). According to MS, the only solution would be a system restore or new installation - both which I would prefer to avoid.
So I will search around a little bit more to try and find something out in order to avoid it. After having invested a good 20+ hours into setting the system up in the way it currently is, I am not too eager to repeat all the steps over again. Most likely, it will have to do with the visual styles, since I also fiddled around with the system files on that topic.

So, anyway.. thanks alot for the hint - even though it didn't fully solve my problem, I now know at least how to adress it. :)

We need to be sure you are on right version of Windows, and you have picked up correct key.
"
Run winver and tell us version (should be 10586), and post image of showkeyplus, blanking all but last five digits of each key for security.

If you run showkey, and click on the displayed product codes, it will blank out all but the last 5 digits automatically with *. Then take your screen shot. It sounds like your windows 8.1 may have been the core Single Language version and you installed 10 Home instead of 10 Home SL. showkey will tell you what the original version was. https://www.tenforums.com/software-ap...7-showkey.html

alphanumeric said:

If you run showkey, and click on the displayed product codes, it will blank out all but the last 5 digits automatically with *. Then take your screen shot. It sounds like your windows 8.1 may have been the core Single Language version and you installed 10 Home instead of 10 Home SL. showkey will tell you what the original version was. https://www.tenforums.com/software-ap...7-showkey.html

Nice tip re blanking key.

caperjack said:

op,upgrade from win8.1 to win10.therefor they do not need to enter a key anymore when doing a clean win10 install.. just skip past where it asks for the key and win10 will activate itself when finished the install,

OP has already upgraded but it has deactivated. A clean install may help but it may not. MS have been known to lose the activation info on their servers. This happened to quite a few people post 10586 upgrade.

@pakZ
You have identified the issue correctly according to this (XP-related but the premise is the same)...the modifications made has corrupted system files.

Error code 0x80004005

This problem may occur if a file that the Windows Product Activation (WPA) requires is damaged or missing. This behavior occurs if one or both of the following conditions are true:

• A file that WPA requires is manually modified.
  

Workaround for error code 0x80004005


Method 1


... perform an in-place upgrade repair. Make sure that you use a valid product key.

I suspect sfc /scannow and dism /restorehealth may be a good alternative as well to fix the corruption.