This is normally caused by the fact that you don't have an Enterprise Subscription, either update your subscription or comment the Enterprise repo out in /etc/apt/sources.list.d/pve-enterprise.list
Hit:1 http://security.debian.org bullseye-security InRelease
Err:2 https://enterprise.proxmox.com/debian/pve bullseye InRelease
401 Unauthorized [IP: 126.96.36.199 443]
Hit:3 http://ftp.hk.debian.org/debian bullseye InRelease
Hit:4 http://ftp.hk.debian.org/debian bullseye-updates InRelease
Hit:5 http://download.proxmox.com/debian/ceph-pacific bullseye InRelease
Reading package lists... Done
E: Failed to fetch https://enterprise.proxmox.com/debian/pve/dists/bullseye/InRelease 401 Unauthorized [IP: 188.8.131.52 443]
E: The repository 'https://enterprise.proxmox.com/debian/pve bullseye InRelease' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.
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