I have one of those! As you know its hammerless... First, the MAB wont fire if the magazine is not installed! There is a cam that pushes against the magazine to drop the sear.... no mag.. no dropped sear! Second, is the firing pin engaging the sear and staying back when you cycle the slide? Third.. grip (back strap) safety! Got to squeeze the MAB firmly! If your good on the first 3 points... now you need to look at the trigger transfer bar... if it is worn out at the trigger.. (small pin rides in the trigger) or worn at the sear... the sear wont move far enough rearward and drop clear of the firing pin.
I have a post here on TFF "MAB Model D fixer upper" that has a-lot of detailed pictures of the inner working and "exploded" view of the parts....
Hope some of this helps...
Shawn