Rpi and cube orange connection

Hello everyone

I have a raspberry pi4b which I want to connect with a cube orange. I have followed all the steps in the documentations available online and also followed some yt videos. everything is set up properly but I always get a “link 1 down” when I run
sudo mavproxy.py --master=/dev/serial0,57600. Can some please explain how I can solve this issue.

The error :
Connect /dev/serial0,57600 source_system=255
Log Directory:
Telemetry log: mav.tlog
Waiting for heartbeat from /dev/serial0
MAV> link 1 down

Thanks in advance