DNS_PROBE_FINISHED_NXDOMAIN issue after installing fewohbee-dockerized on Proxmox Debian 12 VM

[GarfieldMZ]

I tried to install fewohbee-dockerized twice with the same result (DNS_PROBE_FINISHED_NXDOMAIN) when I use http (Port 80).
First try was an Ubuntu VM on Proxmox Second try was an Debian 12 VM on Proxmox.
The results are the same error message.
When I try https with Port 443, it's works fine!

The container are running:

In the meantime I installed the fewohbee-dockerized on an Raspi 4, which is running fine with http and https.
The problem is probably due to Proxmox. But what do I have to change in or for Proxmox?

Any ideas?

regards
Dennis