I am unable to switch to next song using my car radio and iphone

I have an iPhone 4s with iOS 7.0.2 (11A501)

My 2013 Camry has bluetooth function. So I paired my iPhone 4s to the bluetooth (via CarMultiMedia) in my car audio so I can make hands free calls and listen to music stored on my iphone.

So using my car audio system, I can select BlueTooth and listen to my iPhones songs via the car radio.

This works fine.

However, I noticed just 2 days ago (10/4/13) thats while I can listen to the songs, I cannot change/skip to the next song using the up/down arrow on my car radio.

I installed iOS7 back in late September, and I was able to use the skip up/down to change songs.

Anyone have any clues for me

1. why this function no longer work?

2. How to get it back to work?