Do you get the following error message when running apt update on your Proxmox server?
The likely cause is the instance is not licensed.
If you plan to use the free, community version of Proxmox, open the pve-enterprise.list file in the following location and change its content to this:
# OLD - remove this line: deb https://enterprise.proxmox.com/debian/pve bullseye pve-enterprise #NEW - add this new repo instead: deb http://download.proxmox.com/debian/pve bullseye pve-no-subscription
You'll see the apt update command succeeding next time you run it!