No sound transmitted from phone to doorbell speaker

Hi. Started well with Ring3 but now in the myre of 'Why wont this work?' Everything else is apparently set up OK. I can see and hear from the camera and mic on the door bell (received in the app on my iPhone). But the other way (iPhone mic to door bell) produces no sound out at the doorbell speaker. I've chacked the mic settings in settings/privacy and rhey are switched on. What to do?