That appears to be a Win 7 factory PC that was upgraded by Dell service centre - if you have a backup of the obliterated partition then we can retrieve the key from that, otherwise you are SOL.
Best then to install Win 7 and activate with the COA key - then upgrade to Win 10 for free while it...
Welcome to Eight Forums @Michael Rabik
Haven't heard of Cambridge... is this a MS affiliated outlet (partner?) if not they are bogus keys sold to every Dick, Tom, Harry, Sally and whomever cares to fall for their scam.
Which error messages do you get when trying to activate?
Please delete your screenshot - it shows your Win 8.1 RTM Core OEM: DM key.
What edition do you have installed?
Pro, Single Language etc won't activate with that key.
Please post a diagnostic report and make sure you mask the key under OA3 in the report (if it shows there.)
Hi @Elia (you are from my home town)
Drop me a PM I'll come fix it if you are close by and when I have some time ...
@axe0 I think your reservations are warranted... there is no KMS info, which is unusual for a legit machine... exploits tend to hide that info ( from the /dlv report)...
You can use the Media Creation Tool to get the installation media.
You won't be able to upgrade the existing installation and keep data (thus backup personal data beforehand)
Do a clean install of 8.1 and copy back personal data.
That's all fully legit.
Doing an upgrade on a previously...
Suggest restore the backup.
If it's activated, then upgrade to Windows 10 anyway, even if just to get digital entitlement before MS cuts it off...
Win 10 is OK - I just firewall the heck out of it and only let through what I want.
Yup, blocked key - where did you get it from?
Chances are it was sold to too many and someone has pushed the activation count over the edge since you last activated, as even the spare phone activation count is now history.
If you have a backup of the activated system we may be able to restore...