Bluetooth connected but no sound on FM Transmitter car speaker

I am using iPhone X and use FM Transmitter to connect Bluetooth in older car. Without incident, for many years I’ve played music from my iPhone through an FM Bluetooth transmitter.

Since the recent Apple update to 17.1.1 this has affected the sound. Suddenly I can’t hear music playing. Purchased new Bluetooth FM transmitter but same problem is happening.

I can see the device is connected in my Bluetooth, and I can hear the confirmation tone when car is turned on. But the music/podcast can’t be heard unless the car volume is turned to the max setting in the car. Only then can I very faintly hear the music (and crackling) that it’s playing and connected.

1. It’s connecting to device both in Bluetooth settings and when car is turned on (I have completed a ‘forget device’, restart on/off and Bluetooth on/off)
2. despite never using headphones I’ve also put these audio settings to high
3. ive also put the actual phone volume button to high too

I would like to see if someone has found a solution before I do a reset. It’s pitiful music on the radio and it’s ruined long car rides for me. Thanks everyone.