Other thoughts.
Have you seen the following Microsoft article on errors in activating Windows: https://support.microsoft.com/en-us/windows/get-help-with-windows-activation-errors-09d8fb64-6768-4815-0c30-159fa7d89d85 . Specifically what error is being given when you try to activate?
It would be better to use a release channel version of Windows 11 ARM using either of the tools in the unofficlal guide that has linked to. Preview releases are really not necessary for the vast majority of Windows users (they're designed for developers and enterprises to test new Windows before release and to comment back to Microsoft on new features being considered for Windows).
I haven't heard whether OEM licenses will activate Windows 11 ARM. But there are posts in the Microsoft forums that say OEM licenses will activate anything that retail licenses will. It's just that OEM licenses are locked to the system.
What version of Windows is that OEM license for? There are articles that say that some Microsoft is refusing to activate a freshly installed Windows 11 system with Windows 7 or 8 licenses.
If you didn't get this license from Microsoft or an authorized Microsoft distributor, you should check the source where you got it from to make sure the license is legitimate.