Changing Windows Key did not Work

[rpmtl22]

I have 5 Windows computers with 2 being in my home office. In November 2024 I built a new office computer (CompA - dual boot Win10/Win11). The computer it replaced is now my "second" computer (CompB). The one it replaced (CompC) is dismantled and the parts recycled.

My Microsoft account is not adding my newest computer (CompA) to the list of devices. While trying find out why I discovered a licensing error might be the cause. I have paid for the "10 device" ESU program and need this new computer to be included. Only 4 of my 5 computers are currently being recognized.

My licensing ERROR

I used the (non OEM) Win10 Pro license key previously used on CompC for the new system (A). But I MADE A MISTAKE and it seems I entered the Windows activation key from one of my other 3 PCs that are elsewhere in my home (oops).  Windows accepted it (8 months ago) and I only noticed yesterday (in Activation) that "Windows is activated with a digital license linked to your Microsoft account",  while at the bottom of the screen appears "The last product key (ID: .....) you entered can't be used on this copy of Windows (0x803FA67)".  But the system activated ... why??

I then chose to "Change product key" and entered the Win10pro Key from the discarded PC (which is unique and not used on any other system) and it was accepted. The "The last product key ... can't be used" message no longer appears. 

What concerns me is that when I run Belarc Advisor to report the current Win10 key in the Registry it reports the same key as what was there before and is a key used on one of my other three systems. (I re-ran Belarc on that computer to conform).

Does anyone have any explanation of what's going on here??? 

Should I use slmgr /upk (deactivate) and slmgr /cpky (remove the product key from the registry) to deactivate the system and reactivate using the appropriate key? I'm reluctant to do that as "if it ain't broke" ... yet I need my main computer to be included on the devices support by the ESU program. 

Thanks for any advice.

R

[Tripredacus]

Use slmgr with /ipk and put your product key in that way. If it gives you an error, post that message. 

[rpmtl22]

Thank you for your help :-)

I entered the serial number using "slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX"
(XXXXX = the good Win10-Pro key) and I got:

Error:  0xC004F050 The Software Licensing Service reported that the product key is invalid.

But I know that it IS valid and came from previous 2 retired systems. The first was a upgrade from Windows 7 Pro in 2016 and the second was 6 months ago. 

Meanwhile the system claims to be activated without any error messages after entering it in "Change product key".

Strange ....

R

 

Edited 1 hour ago by rpmtl22

[rpmtl22]

Update:  After using the methods posted on the web (on various sites) to force the Consumer ESU activation prompt in System Update I successfully included this PC in my family of 5 computers still running Windows 10. This computer is my main PC (dual-boot Win10/Win11) and I really need it to continue getting Win10 security updates.

I might just ignore the licensing mystery as signing this PC up for the ESU program was my main objective. 

FYI I'm a photographer who still uses old Adobe CS6 apps which Adobe (intentionally?) disables when installing Creative Suite 2025. My workaround is to use Win11 with the recent CC apps and use Win10 for CS6 apps which I still need access to for editing older files and to use features that no longer exist in CC2025.

R