Waeco camera to LCD screen

I've just upgrade the camera in my horse float to a Waeco Perfectview Cam 27 (RV-27/N). Including upgrading the wiring to suit. I previously used Waeco connectors between the float and the ute, so I re wired them to suit.

I have a generic in-dash LCD screen that has an RCA input for the video.

The old camera only needed four wires; positive and negative 12v and positive and negative video feed. I rewired the ute plug to suit the new camera; positive 12v to power in (connection 5), both negatives to the common negative (connection 7), and the video out on the camera to the old video in on the screen (connection 4).

However, when I plugged it together, I got no signal to the screen.

I plugged in another tow vehicle (that has a Waeco screen) and the image from the camera worked in that. So the float is wired up ok.

Does anyone know how you can hook up a Waeco camera to a non waeco screen?

thanks