Alexa rings but cannot answer door: Device not found?

Hi there, I have just bought the classic ring door-bell integration and am trying to make it work with Alexa. I have set it up with Alexa, so that it will inform me when somebody rings. That works fine. Alexa also lists the device in the Alexa app under devices. However, I cannot get it to open a voice channel to the door nor unlock the door. Alexa claims that it doesn't know the device. The conversation will go sth like this (from memory and translated from German): Alexa: "Somebody has rang at ". Me: "Alexa, speak with " Alexa: "Sorry, I cannot find a device or contact called " Me: "Alexa, unlock " Alexa: "Sorry, I cannot find a device or group called " Me: "Alexa, what devices are connected?" Alexa: "This feature is not yet supported" - The device is configured as both in Alexa and in Ring. - I have removed skill and device and re-added it. - The device configuration in Alexa suggests to start with "Alexa, speak with ". - I can open and answer the door using the app. - Alexa can access the internet to play music or answer questions. - I have tried different words for but couldn't get it to work. Any ideas, what else I could try?