I have a third order system i need to control using MATLAB, Simulink. I have tried the Discrete PID block and the autotune but the system is unable to track d reference. Help

I have a third order system which i converted from state space model to a transfer function model. The open loop response using the step signal was simulated with no issues at all. Howerver, when I tried to control the system using the discrete pid block in simulink, the system was unable to track the reference including the autotune feature. I need help on how to solve this problem