Are you using an Apple product that has the new 8 pin connector? And if so, are you using an Apple brand USB cable to make the connection to the bike?
I'm asking cause I had a similar issue with my iPod and iPhone 6 with the Iron Cross iPod dock. Found an article where they talk about how Apple does things differently with the new 8 pin connector.
Long short story, only way I got it to work is to not use a generic connecting cord. Not sure of the difference, but it worked flawlessly with the Apple cord.