Checking out a new batch of ARM Stamps, I plugged a new one in and all that I saw was unknown USB device.
What did I do wrong, checked a couple more and the same thing.
SOooo... went back to an older Stamp out of inventory and the same issue.
OK like I tell people type a question into Google. It led me to an issue with the Windows Registry.
Turns out some Windows update changed a registry item (even changed names a bit). But in the current version HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\DeviceGuard\RequireMicrosoftSignedBootChain was set to 1, and needed to be set to 0.