If it's not working either the process is still in it's infancy, it was incorrectly applied or their is mis trust in the organisation. Crew will be gun shy to report fatigued if management has previously made examples of other crew.
My only example of calling in too tired to operate a couple of years ago (due to serious hotel issues for which a formal complaint and report were submitted) for a major iconic Australian airline with a marsupial painted on its tail, was an unpleasant experience for several days afterwards. Fortunately it was eventually sorted out by some very blunt phone calls from one of our pilot association scheduling reps.
Regrettably you can't stop d*ckheads from floating into positions of managerial power.