Model predictive control for a simple tank

Tried to design an MPC strategy for a simple tank (SIMULINK: watertank). While defining the MPC design, though proper trimming points were obtained (verified by hand), while selecting import, I get the following error:

Simulink model 'simpletank_mpc' was called with an invalid flag

Component:Model Predictive Controller | Category:Linearize Model error

Can someone help me resolve this issue?