Hi @Frank_Remmert,
Thank you for your patience and I do apologize that it’s taken several days to respond.
I see from the screenshot you’re using a Fritz!Box. Provided you don’t have a second router in your setup and just the repeater, then I recommend you try setting a manual port forwarding rule in the Fritz!Box web admin. Here are some step-by-step instructions: Port Forwarding Instructions for (Most) Fritz!Box Users
The diagnostics indicate a UPnP failure with auto-configuration. The manual rule should allow for the Core to reach the internet safely through the port on the router without relying on UPnP. Please let me know if you have any difficulties and we’ll be here to assist.