I am seeing a problem working with a Teensy 4.1 on an Intel NUC running a recent version of Win 10. Basically, I cannot connect to a T41 that was already programmed with an application that talks serial USB. Further when I try to program the T41 from the NUC (using teensy.exe and a .hex file that is good), it hangs up with red LED next to the USB connect on. If I repeat the processes with a different Win 10 machine, it works fine.

I tried different USB cables to no benefit.

The odd thing, it was working ok for serial USB connection but then I tried to program the T41 with teensy.exe and got the red LED hang. After that even serial USB didn't work. I swapped to a programmed T41 that works fine with another Win 10 PC and got no response. Is there some driver issue I need to deal with?