OK the first thing to do is to see if there is power going to the H-bridge driver. Put your voltmeter on pin 13 an pin 16 and see if you have a voltage here. This is the motor supply.
Then check that there is a voltage between pin and pin 8 - this is the logic supply.
Pins 1 & 9 are the enable pins, these have to be high before a motor will turn. Is this connected to an arduino pin? If so that pin needs to be set to be an output and driven low. That is currently not happening in your sketch.