2007 Liberty No Sound from speakers

[9siesrock]

I recently bought my son his first car 2007 liberty wagon, the audio system puts out no sound. It occasionally would work for a short period.
I replaced the internl amplifier in the Kenwood head unit thinking that it must be the amp.. nope.
We have installed a new carplay unit where the Nav unit was, the wiring loom is connected to the Carplay unit and bypassed the factory unit completely and still have the same issue. The sound has worked a couple of times but now not at all.
There is no amplifier under the seat.
I would think maybe a dodgy earth for the speakers but there is no intermittent issue after powering up, it either works for a bit then goes silent or not at all.
Can anyone please help??