If you find a mass-storage drive like D: the KitProg3 is recognized as an mbed Composite Device. Please confirm the device manager selecting the menu item "View>Devices by connection".
In this mode, the STATUS LED blinks fast (2Hz) and the Modus Toolbox failed to find a CMSIS-DAP device.
Please push the MODE switch once to change the mode to KitProg3 CMSIS-DAP.
In this mode, the STATUS LED stops blinking and turns on stably.