I have looked at the instructions on line and there are a couple of pointers.
Have you set the film type to 120 or 220?
Have you removed the darkslide?
When loading the film it seems you have to manually move the film forward the film before the back is attached to the camera. This only a small movement until it clicks twice.
I am not familiar at all with the Mamiya AF cameras so cannot go any further. I hope this helps.
Yes, Yes, and Yes. Nothing happens in terms of film advancing.