Mecool M8S Pro L - AV Cable not working



I have recently bought a Mecool M8S Pro L but the box only seems to work on a HDMI output?

I’m setting it up for a friend and they have a system where the AV cable needs to be used. Previously, they have had a MAG box and it worked well (so I know it’s wired up correctly), but when I unplugged it and put the M8S Pro L in place, no video or sound output was showing.

I was concerned it was an issue with the box but when I put the HDMI cable back in it worked fine.

Can somebody help me fix this? Do I need to change some display settings on the box before I use the AV cable?

Thank you