Not moving motor with MD04

Hi, I have connecte an MD04 to control a motor. I have plugged it to a raspberry by USB… I have written a short code in python and using pyserial and I am able to set/read baud rate, operation mode, etc. but if I set speed or acceleration it does not do anything, register does not change. I measure voltage V+ and G and I have the right reading but M-M is always zero
I have checked motor and it is working if I connect it directly.
I am using the addresses located at datasheet of MD04, but setting speed, acceleration or direction does not seem to work. The others work fine. Can you please tell me what I am doing wrong?

Hello @winter1 and welcome to the forum.

From your post, seems that you used this controller:
And you used this datasheet:
Which motor did you use?

It would be good if you can post a scheme and a photo of your wiring and also your Python code!