Copter 3.5.1/ pixhawk 2.4.8 won't arm?

Hi, i just flashed copter 3.5.1 on a tricopter frame (titus 600) with pixhawkk PX4 2.4.8 ( from banggood). With the new firmware i can’t arm the motor. The yaw servo received informations and move to center ( 1500) .The LCD screen on board and mission planner via USB don’t give information on non arming reason. The pixhawk don’t emitted non arming sound.
I can test the motors and servos via mission planner test pannel and all 3 motors and yaw servo are working. I do not enable FENCE.
I am also unable to downgrade to copter 3.4.6 version ( mission planner do not recognize the pixhawk?? but i am able to connect it via mavlink)

Any idea to help me


This happened to me when I put the first 3.5 rc on. I had to redo the radio setup and calibration on my FCs and everything was fine.

Can’t say this is your issue for sure but it’s worth a check.

Also was having the mp not recognizing the pixhawk after latest MP upgrade. Make sure your com port and baud rate are selected for the FC.

Thank’s Lance for your help.
I finally was able to downgrade the PX4 via QGgroundcountrol. Then re-install copter 3.5.1. with MP. Use the wizard to re-calibrate the copter. Recalibrate radio on more time and …YES… able to arm. Perseverance pays :slight_smile:
Waiting now for good weather to test the copter in flight an test the autotune.