No Connection from Device - Error

[Daniel-WW]

Hello, I have tried Antennas in various ways. Once on Docker, which runs on a Synology NAS system, and once on Docker, which runs on a Proxmox server. I can connect to TVHeadend every time. The Antennas server is also displayed on my devices (smart TV, tablet). However, as soon as I try to connect from the device, I get an error message. I cannot explain why this is happening. Streams cannot be played. A FRITZ!Box is used as the router. I have already considered whether there could be a problem with the transmission protocol, but I do not know which settings I need to change. I would be very grateful for any help. Best regards, Daniel