Waiting for Mavlink Heartbeats

Hello everybody!

I am building a drone for my thesis at my degree and I am having some difficulties configuring the MiniOSD. I am using a Pixhawk 2.4.8 flight controller and a Mini OSD. I have set up everything including updating the drivers and firmware of the OSD using ArduCAM but I keep getting the same error “Waiting for MAVLink heartbeats”. I have also tried enabling the OSD in Mission Planner but it seems not to de anything. I have also tried changing the TX and RX cable but it keeps the same.

Do you have any idea on how to solve it?

It will be very usefull if you can help me