Need help with HITL setup

Dear all,
I’m having issues with the HITL setup. I followed the guide here. But couldn’t get it to work nicely. Here is what I used:

  • Cube Orange and pixhawk 4 autopilot
  • Different versions of the PX4 software (dev/stable/old stable)
  • Latest jMAVSim and QGroundControl

Following the guide, I tried the HITL a lot of times (with different versions of PX4 and different autopilot). I only got it works for 2/3 times. In most of the case, after I started the jMAVSim, the MAVLink connection between the autopilot and the jMAVSim cannot be establised. I added some print in jMAVSim. It seems that no MAVLINK data is recived by the simulator.

Is there anyone can provide some tips about how to debug/fix this? Thanks very much.