Grey page after installation

Hello

I installed a Jitsi on a ubuntu 18.04 server on a Hetzner cloud and followed https://community.hetzner.com/tutorials/jitsi-meet-on-debian-ubuntu. went pretty straight forward. But I just get a n empty grey page (In Safari, Firefox and Chrome) you can see https://meet.sepphod.de
the ports 80,443,4443 and 10000-20000/UDP are open.
Any support is welcomed

thx

Sepphod