DDJ 800 No Sound on Line Input/External Inputs

I'm trying to connect my iPad to my DDJ-800 using the line in on channel one and or two, but I'm not getting any sound?

It works on the AUX input, but not channel 1 or channel 2. I've checked the connections at the back and they are set to LINE (not phono) and I've switched the switch at the top from Deck 1/2 to Phono/Line.

Any ideas? I'm sure it's a software setting, as I've had this working before!

Thanks in advance.