Mission Planner cannot detect Pixhawk

I am running the latest Mission Planner on Windows 10 on a PC.
version:1.3.72 build 1.3.7463.24854

I have tried 3 different Pixhawk Modules and all fail in the same manner.
I have tried 2 different USB cables; no luck.

A much older MP version on a Win 10 laptop does easily recognize the Pixhawks.

What am I missing?

please try MP beta. i think there was an issue with devices that have an old bootloader on them

Hi Michael,
I cannot find a Beta version on the web anywhere so tried the “check for Beta updates” in MP.
That method always fails saying a DLL is being used by another process.
I rebooted the PC; no luck.
Any ideas please.