Activate Failed after rebuild

I just completed rebuilding my desktop with Windows 10 Pro

Hi, have you changed items other than disk and RAM?

I purchased the software years ago (Windows 8)

was that a full retail license or something else?

Please run
Showkeyplus (free) and post the result hiding any actual key details.

Is your activation linked to a MS live id account?

Try:
Use Activation Troubleshooter in Windows 10

from the Tutorial section, which I encourage you to browse and search. There's more on activation, for example.

If I have to buy an new license where can I get the best price for a real version of the software.

There's a renewed magazine-based offer posted again recently, but I think increased from £40 to £50 for win 10 Pro.
Others have obtained cheap (valid - care!) Win 7 or 8 keys and used those.

Various discussions on that if you care to search tenforums.

Where did you get the key from?

I bought Windows 10 Pro this month, too! Glad I did! (from Staples, like I did for Home in 2019, which didn't start getting used until January 3, 2020, with my first Ryzen build) (IIRC, it was a bit less expensive than that)

I said adios to Home, just this month!

Johnml said:

Thanks RJARRRPCGP, may I call you "R"

Definitely yes!

Johnml said:

Thanks RJARRRPCGP, may I call you "R"

I think OP must be a 'droid' and should be designated R4P2.

Johnml said:

I give up! I just went and bought a new version of windows 10 pro for $199. It’s worth it not to try to get anything out of Microsoft. I appreciate the feedback. Now my new build is complete and up to speed. What a difference. Asia Prime Z590M-pro I9 10900 32 Gb ram 1 Tb name. It flies.

Thank you for your reply.

Johnml said:

I give up! I just went and bought a new version of windows 10 pro for $199. It’s worth it not to try to get anything out of Microsoft. I appreciate the feedback. Now my new build is complete and up to speed. What a difference. Asia Prime Z590M-pro I9 10900 32 Gb ram 1 Tb name. It flies.

It's a pity you didn't read this thread which inspired me buy a W10 Pro key for c. £10. How can I upgrade from Retail Home to Retail Pro at cheapest price?