Doorbell won't answer on echo show

When the ring video doorbell (2nd gen) is pressed, the echo show chimes and alerts that somebody is at the front door with a muted live video display. When prompted to answer the door, "waiting for ring.com" shows and then cuts out showing the echo home screen every time. The blue light on the doorbell also cuts out at that point. Yet the doorbell answers without issue with video and sound on mobile phones . Video and audio are also working fine when Alexa is asked to answer the front door without the doorbell being pressed. This has being going on for the last month or so. We've tried resetting the ring, unpairing the ring skill and reinstalling the app to no avail. Speaking to an assistant also got us nowhere. Kind of defeats the object of having an intercom doorbell if you can't respond at either end! Anybody else having the same issue ?