I am trying to use Genetic Algorithm to optimize my agent-base model in anylogic. However, I got this error: NullPointerException. It seems my model cannot read the objective function, which is the total coat.

I am trying to use Genetic Algorithm to optimize my agent-base model in the field of supply chain management. However, I got this error: NullPointerException. It seems my model cannot read the objective function, which is the total coat. On the other hand, I tried Optquest as well and learned that it works. my problem has 22 decision variables which are related to the order-up-to level inventory policy. I want to the get the optimal values for minimum and maximum inventory levels related to this policy, while cost is minimized. I would appreciate it if you could guide me what the problem is and how I can fix it. Thanks!