Tilt motors don't tilt at all

Hi, I’m an engeneering student and I’ve a big problem I can’t solve by months. I’m building a QuadPlane (4 motor, with the 2 ahead tiltable). I’ve set the Q_FRAME_CLASS as a quad, Q_FRAME_TYPE as a X frame and I’ve set 5 to Q_TILT_MASK for indicating the two tiltable motors. I’ve also set the servo output (with 75 and 76 values) so I can see the assigned functiones under Mandatory Hardware/Servo Outputs window on Mission Planner. What I see through that window is that the two channels have 0 PWM signals as output. And If I change between the different flight modes the 2 servo motors for the tilt do nothing. At all. PWM values remains stuck on 0 too. I really have no idea how to overcome this problematic situation. I would really enjoy if somone would gently reply this topic giving me some support. Hope to enjoy the discussion soon. Thanks to everyone.