Windows 10: Windows 10 Pro transfer

Hi,


I recently upgraded OEM home Windows 10 to Pro, through the Microsoft Store. Order went well, download, install, activation went well, and has been working ok for last couple of months. Pro version is showing as retail.


Now I have a new machine, with OEM Home version on....what I want to do, is transfer the Pro upgrade to the new machine and revert the old machine back to it's original Home state. From what I've read, as it's a retail version of Pro, it should be possible to transfer.


I've trawled back through emails, and when I upgraded I was not issued a digital licence key, but both machines logged in with same MS account show their respective versions are activated with digital licence linked to my account.


I've tried a few things, but is there an easy way of doing this, surely it should be pretty straightforward a 1 for 1 swap??

:)