I can’t add my Echo Show devices as security cameras in the Ring app

I connected successfully Alexa and Ring using the respective accounts. I’m also able to control the Ring security system from Alexa and I see all the Ring security devices on the Alexa app. However, I’m not able to connect the Echo Shows in the Ring app. I always receive the error “there are no supported devices in your Amazon account”. Of course I have already enabled (and re-enabled a few times) the Home Monitoring setting in the Echo Show 5 and they are recognized also by Alexa as cameras. What am I missing?! Thanks a lot for your help!