Windows 11 not activating after mainboard replacement, troubleshooter doesn't run, can't get support

TannerOakridge​, sorry for the delay. I took some days to reply because not only was I busy with a large work assignment, but also because exactly for that reason, I needed my PC working (which it was and is, other than the watermark and the black desktop), and updating a Windows install always involves some risk.

But eventually, I followed your suggestion and reinstalled Windows 11 over itself. It didn't work. The activation troubleshooter still doesn't load, and nearly all the advice I can find on forums and such involves using the troubleshooter. I couldn't find any case in which the troubleshooter didn't even appear, as is the case with me.

I have also found some tips about restarting some Windows services and using PowerShell commands. None worked. Also, most of the advice is very old, as I found several suggestions for calling Microsoft's telephone activation, which has no longer existed for quite some time (that was how I resolved my previous activation issues due to hardware changes).

And it gets worse: even if I paid for a new license key, I wouldn't be able to use it: the Change button in the activation window, for changing the product key, which is what I would have to use, also does nothing when clicked.

It looks like I'll have to do a clean install of Windows to try to resolve the issue. This means that I'll have to cope with the non-activated system for a while, because that would be a major disruption to my work for at least a couple of days, until I reinstalled and reconfigured everything — and with no guarantee of success. 😞 I can't afford to do that right now. The worst of all is my inability to get any support from Microsoft. That's a HUGE disappointment, I feel betrayed and abandoned. 😠