Ring doorbell appears in Alexa App but not on any Echo Show device

I've just installed - and, for that matter, completely removed and reinstalled - a Ring 4. Whilst it's working fine with the Ring app on a couple of smartphones (Android and Apple), it's not playing nicely with the five Amazon Echo devices in the house (five Echo Show 8 with video and two-sound only Echo Dots). The devices simply don't know "Front Door" even though that's exactly how it appears in the Alexa app after getting it to work within Ring and then adding the Ring skill to Alexa. For example, my app says I could say, "Alexa, talk to the front door", but if I do it responds with, "I heard you ask for the Front Door, but I can't find that name in your list of contacts or devices."Based on the videos I've watched, I was expecting that the settings I've used would ensure that when I pressed the button a live video feed would pop onto the Echo Shows' screens and an announcement would be made on all the devices. But that's simply not happening. I have, of course, seen lots of comments from people saying only the announcement are possible and that video has proven to be problematic ... but I'm not even getting that far! So I'd love some advice, please.