You are almost an NCO, first read the order MCO 6100.13A I believe is the most current, and see what applies to you. Second verify that the failing score was run, if it is not in MCTIMS then is never happened, I would talk to your training NCO. Requesting MAST is a right that is afforded to all Marines I recommend gathering all your info and and going to your 1stSgt with your platoon sergeant if he stills says there is nothing he can do for you then request mast. Once you say those magic words he is required to run your request up. I would follow it all the way even if he does offer to fix it once you say that. You are the one who cares the most about your career, if you are planning to stay in I recommend you start reading Marine Corps Orders gunny google can help you find anything you need in that department.

If you want to be an NCO learn the rules and play within them, you will need to know them to advise your Marines once you pick up.