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?