Propeller can not be driven by "net_fdm Packet for FlightGear" block in Simulink

[shaopengyuan]

Thank you for the MQ-9 model can be used in FlightGear, It help me alot in my research project.
But I found an issue these days.
When I use the "net_fdm Packet for FlightGear" block to drive MQ-9 model in FlightGear, the propeller can not spin after setting RPM and engine status in the input.
After several days of research, the issue still can not be resolved by my.
Do you know how to solve this problem @meirm @JMaverick16