Ok used massive dev chart and reduced time from 6min dev to 3.30 dev
Save your money, it's not the developer
Sounds like you havent put the film in the camera properly
Manual cameras don't tend to complain about film advance, i dont have a FM2n so i cant go into specifics but i assume you need to hook the leader into the spool on the right and advance the film one shot to make sure it's hooked
I'm sure a FM2n user will come along soon