[Alan Anderson]

I don't recognize those icons, but I'll give what suggestions I can.

It's possible that your rectangular-to-polar conversion gives its output angle in radians, while the mecanum drive wants it in degrees. This would make you always travel within a few degrees of straight forward/reverse.

Mecanum wheels need to be set up so that you can not grab the robot and spin it easily by hand. The contact between the rollers and the floor should make an "O" or diamond shape. (If instead it's in an "X" shape, the robot won't be able to turn very well under its own power.)