Hi,
I have my own PSU 5V that goes to the motor shield VCC and GND, I then run the GND from that to the arduino. I can see the outputs are correct for my motors ie low and high for IN1 and IN2, and HIGH for ENA (speed - I pass 200 in here from s/w and I use a PWM pin from the arudiono - analogue).
So I know my wiring is good (is swap an uno in and it works, I kow my software is good same thing swap an uno and it works), but when I put on the mkr1000 I can see the signals on the pins are still good (test tehm with a led), but it will not switch the motor shield ?
What is weird is if I hold the VCC 5 volt cable in my hand and press it, the motors come on !!!