UPDATE:
Sadly, connecting the iPhone only temporarily solved the issue.
Once the Android phone is reconnected, there is audio until you turn it down - it won't then turn back up! So I reconnected the iPhone and all was fine again. Back to Android and, sure enough, there was music, but the volume wouldn't increase, only decrease until there was silence.
So glad I ordered my speaker upgrade this afternoon...
Sadly, connecting the iPhone only temporarily solved the issue.
Once the Android phone is reconnected, there is audio until you turn it down - it won't then turn back up! So I reconnected the iPhone and all was fine again. Back to Android and, sure enough, there was music, but the volume wouldn't increase, only decrease until there was silence.
So glad I ordered my speaker upgrade this afternoon...