apt-get update exit code 100 after 8 to 9 upgrade

[optical]

In addition to the tty errors now I have this red bar showing up as well in the Tasks area at the bottom. apt-get failed, code 100

 

[leesteken]

Code 100 can happen when the enterprise repository is activated (which it automatically is after such an upgrade) and you don't have a subscription key. Check your repositories in the Proxmox web GUI and/or the manual: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#sysadmin_package_repositories
If this does not resolve it, please show (in CODE-tags) the output of apt-get update, from the Shell or command-line or SSH, so people can investigate the actual error message.