AUX jack doesn't work

This is actually on a 2010 Corolla S I just bought for my daughter. It's the basic stereo, has AM, FM, FM2 and DISC/AUX buttons below the channel display and is a single CD player. The AUX jack is down to the left. It's the same basic stereo that my 2011 Tacoma has. Everything works perfectly except the AUX jack; when she plugs her i-Phone into the jack to play her music, nothing happens, the radio keeps playing. Pressing the AUX/DISC button does nothing. When she presses the 'mode' button on the steering wheel to change from AM to FM to FM 2 to AUX/DISC, it skips AUX/DISC.

Could this be a fuse issue, or something more involved? Is this a sort-of common issue, or a rarity?

 

Possible that Aux Input Socket is worn out from over used from previous owner. If the Aux Socket worn out, when user inserted Aux Jack, the tip or sleeve never contact with worn out Aux socket connectors inside. If no contact then the radio never detects the Aux input which never toggle the AUX option.
Easiest way is replaced with a new Aux cable harness. Other option is rebuild the Aux Socket which required soldering and ...etc.

Happened a lot with iPods.