Windows activation confusion

I recently reinstalled Windows and suddenly started getting activation messages. I’m trying to fix it, so wondering what options people use when they don’t want to buy a full license again. Feels like this happens more often than expected actually.

Went through this last year after reinstalling Windows on my old desktop. Everything looked fine at first, then the activation notice showed up and wouldn’t go away no matter what I tried. I kept seeing people mention a kms activator in different threads, so eventually I gave it a shot out of frustration. In my case it actually worked and stopped the reminders. It got me unstuck when nothing else did.