Something to remember. I have two Proxmox nodes in a “cluster” so that I can access both from a single UI. If one node is shutdown or goes offline, I may not be able to modify the properties of a VM or container.
The symtpom is a 500 error message. and the fix was found and it’s simple.
Just needed to run this command on the node that’s online: pvecm expected 1
Have a good weekend!