On my Desktop Computer I moved from Win 7 to Win 10 at the time it was free ( more than 1 year ago )
When I use Speccy to get the information on my Operating system , I get Windows 10 Professional , and installation date , but the " Product Key is wrong " ( tested with many other tools )
The serial key is the unique identifier for that piece of software, where was the license/product key is just a code that unlocks the software to make us usable.
In other words, the serial key is like your address, but the product key is like the key to your front door.
Have a look here for some explanations about keys.
If you are re-installing Windows 10 on the same machine you will not need to enter a key. Microsoft will already have it stored digitally (known as digital entitlement)
the end user has never needed to know their 'serial key'.
another 'key' MS shows us is the Product ID shown in Control Panel, System, which is calculated from the Product Key.
MS only uses the Product Key (or activation key) found on the CoA (Certificate of Authenticity) sticker, either already stuck to the PC or on the Windows software packaging.
and it's that key that is used to install, activate, re-activate, or upgrade Windows.
also, this Serial Number Speccy shows, why is it in the format (xxxxx-xxxxx-xxxxx-xxxxx-xxxxx) of a Product Key if it's not the Product Key!
the Product ID is in a different format, usually with -OEM- in the ID but Win10 has changed that.
my suggestion, if the thing Speccy is showing isn't the Product Key, then it should be.
I can't vouch for Speccy under Windows 10 and this serial key thingy, but definitely a year or two ago there was a post from a user claiming that Speccy's Product Key (yes, Product Key) didn't match another software's extraction of the key.
I think Piriform must have fixed it or released a new version, whatever, but there was a time in the past where the 'key' supplied by Speccy definitely matched my Windows 7 installation of the time.
Anyway, if it doesn't now, it doesn't - it is what it is.
Probably not what Speccy should be showing anyway. Stick to the hardware specs.
Have a look here for some explanations about keys.
If you are re-installing Windows 10 on the same machine you will not need to enter a key. Microsoft will already have it stored digitally (known as digital entitlement)