I had this issue and the solution to my problem was that there is a spring inside the transmitter that no longer was pushing the outer pin all the way out and therefore no longer completing the circuit. To resolve simply open it and with some needle nose pliers pull out the spring and reattach the cover this time the pin will reach and turn on. I hope this helps.

Try raising the volume on your phone to the max, it should come back on

I have this problem currently and was wondering if you have found a solution yet?

Same problem with mine a couple months after purchase.