[Mark McLeod]

There is a little anomaly in Begin.vi with both
- the constants for PWM 0 and PWM 1, and
- the Inverted flags

They still have the labels from previously being part of an Open 2 Motor.
I'd recommend that you delete those four constants and do a create constant for them again.

After you've gotten new constants there, turn on the label for each of them by hovering the cursor over them and right-clicking to get the popup menu and choosing Visible Items -> Label (You can drag the labels around to better places too if you would like.)
With the Open 4 Motor there are also two more Inverts located along the bottom edge of the Open 4 icon that you need to create constants (and labels) for.

An issue is that because you had constants left over from the 2 Motor, they reverse only one of the motors on the left side (I think the left rear). So the left side motors would be fighting each other.

So, make sure to Invert both Left side motors (make them T for true).
If when you test the robot you find that the front and back are reversed, then just reverse all the Inverts and make the Left side motors False and the right side motors True.