Gpg4Win currently supports x86 (32-bit) and x64 (64-bit) Windows. For some time now, Microsoft has been working on Windows on ARM64, most recently with their Surface Pro X range of devices.
It would be rather great if Gpg4Win could be released for Windows on ARM64 and this issue is essentially a feature request: Bring the greatness of Gpg4Win to Windows on ARM64 users.