Current is 1,2 A, this is about 330 RPM ?
Stepper motors are driven by steps or pulses (that's why they are named stepper motors).
The current determines the torque at a given speed, but you can't drive a stepper by just controlling the current
and the current needs to be pulsed and each pulse causes the stepper go one step (in full step mode).
Did you read Robin2's two links about steppers?
Your motor needs far more current than 1,2A. The datasheet talks about 3A!
Normally it will already turn at that value but you won't get the torque that is possible with your motor.
1. please set the driver settings to "full step" = 1/1 mode (dip switch settings)
2. set the current limit to a value close to the power supply's limit - if you can go with another power supply which can deliver 3A or more (at 24V), you could e.g. set the current limit to 2.5 or 3A - but not more!!
3. Run either Robin2's simple stepper sketch, which needs no library or go with the one which I posted - but you will need the AccelStepper library for that sketch. Don't forget to adjust the step/dir pins to the ones which you are using.
When the stepper works after having used the AccelStepper library sketch, you can play with adjusting the microstepping. But: microstepping gives you a smoother run (and noise) of the stepper motor, but it will decrease the maximum speed. Look at the example in my previous post.