We are decomissioning a few of our older latitudes. Mostly 7470 or 7400s from the 2018/2019 era. All of the latitudes I'm working on were purchased with Windows 10 Pro, and we've never had to enter a product key - either the key was autodetected (embedded in the motherboard), or was possibly never autodetected because we've been using Microsoft E5 licensing recently. But some of our latitudes have had the motherboard replaced, and that's where this issue seems to start.

After completely wiping and using Dell SupportAssist OS recovery to reimage Windows 10 the physical license keys that came with the motherboard replacements won't activate. These are sealed envelopes that had the Windows Key covered by a sticker. Admittedly I didn't keep track of which windows key went with which laptop (we've had several motherboard replacements over the years), so I have a drawer with a few dozen replacement Windows 10 keys that were never opened but are all similar. When I'm trying to activate any of my systems that had a motherboard replacement, unsealing and entering one of these license keys results in activation failure with Windows recommending I go buy a valid license from the Microsoft Store. I've tried several of my sealed replacement keys and they all fail activation.

I remember the service tech handing these to me at each motherboard replacement and I tucked them into my drawer of goodies. They've never been unsealed, I had to tear the envelope open to get the key out from behind the sticker. They are generally a few years old, but these should be valid keys and so far none of them will activate. Is this a Dell issue or a Microsoft issue? What's the right way to proceed?

It's also tricky because I don't remember which machines had a motherboard replacement, so I'm just trying to use these as I come across a system that won't autodetect a Windows key. But none of them seem to work.