Activation after reinstallation

Kent

Hi,
I received 6 Beelink BT3 Pro boxes the other day.
5 worked perfectly while the very last didn't want to boot and run the mini setup correctly :(
I found this image, https://mega.nz/#!P2JjjApL!R7rtr ... UYvnErM7b0zllBhD_tw, which I installed on the box.
All worked perfectly, thanks Beelink.

But unfortunately this single box now asks for Windows Activation. I have tried "slmgr /ato" which didn't work. It refuses to activate, and I therefore have a constant "Active Windows" in the right bottom corner of the screen.
What did I do wrong here? More important, how can I get this single box activated?

Regards
Kent