No priority (or zero) specified for pin - apt update / apt upgrade is not working anymore

Hello All!

I need help with my Proxmox VE. This morning, I started getting the message "No priority (or zero) specified for pin" when I tried to update/upgrade my system.

My apt-cache policy shows this:
apt-cache policy
Package files:
100 /var/lib/dpkg/status
release a=now
500 http://download.proxmox.com/debian/pve bookworm/pve-no-subscription amd64 Packages
release o=Proxmox,a=stable,n=bookworm,l=Proxmox Debian Repository,c=pve-no-subscription,b=amd64
origin...

Read more