Getting players to learn new PPM's

I'm still playing the demo version, and so far have had 0% success when asking players to learn new PPM's, even when these are clearly to that player's advantage when considering his attributes (e.g. getting a pacey forward to attempt to break the offside trap).

Is manager reputation an issue when seeing if the player will listen to his manager? I assume the player's age can be a factor (more difficult to teach an old dog new tricks ), but even youngsters have outrightly refused to learn any moves so far.

Anyone else encountered this in their games, and any tips on how to approach the problem?

I seem to have about a 50% success rate when asking. Seems pretty random to me.