Core isn't configured for access outside

[Rugby (aka Daniel or Big Dan)]

@5ORYN

Vodafone German

I would check with your ISP but I think they use a CGNAT and don’t provide connections which can use Port Forwarding via IPv4.

See this thread: Vodafone Germany: No port forwarding for home accounts. DS Lite Tunnelled IPv4 address that doesn't do port forwarding. [NOT Resolved for Most Users; See Posts. Roon Investigating]

If this is the case, you might be able to setup a unsupported work around with Tailscale VPN.