Aux not working in my vauxhall vivaro van?

I'm having trouble trying to work my aux on the stereo in my van. I have had it working a while back but can't remember how i did this? I just received an aux cable from ebay today and plugged it into the aux port on the standard vauxhall vivaro cd player and pressed source and all it could find is fm and cd. I have tried holding it in etc but no luck! I'm using an iphone 5. Please any help appreciated its giving me a headache!

This is a guess, but I have seen it happen before.
If you use that jack alot, or hang the cord down with the phone ( like having it on the seat next to you )
It is possible to snap the small solder tabs, connecting the aux, to the mother board in the radio. If it's a poor soldering job, then it's possible. Plus putting the cord in and out can also pop that soldered connection. It's usually a very fine solder, as the leads going from a 3.5mm jack are obviously small, like headphone wire.
If it's not that, there might be a "settings", to turn the aux feature on. Some radios don't have that setting on "factory", like if the battery was ever disconnected… Try holding some of the buttons down, for a few seconds, maybe you can get into it somehow ( I've never played with a Vauxhall, or even seen one here in the US… )