Ok so, up until yesterday all was good, I have a Ring doorbell connected to an Echo dot and Samsung TV, up until yesterday I would ask - Alexa show front door and it would show, BUT yesterday it suddenly says Sorry Cameras dont work on this device ??;really as it did till now, called Amazon after an hour of trying this and that still no further forward please help 
Hi @ELOise. Start by checking to see if all of the related apps are up to date with the latest firmware. Next, try to unlearn the Ring Skill, Close the Alexa app, the learn the Ring Skill again. Let me know if this helps!