THANK YOU!! It had not occurred to me to turn off signed driver enforcement (there is a lesson to be learned there…) and it’s really ironic that Sparkfun had the solution (workaround, really) all along. I just tried this on Win10/x64 and it works. Woot! The Windows UI for this is abysmal, but I made it through even though it looked at times like it was going to fail with all the required reboots).
Ironically, I had just come up with a workaround for this today (posed on github) where I forced Windows to think the ProMicro was an Arduino Micro, but I was advised that this hack would be inadvisable on a 3.3V ProMicro. So now, I have a solution that works for both. Thanks for taking the time to post this solution. Props…
RD7