There are many reasons why Proxmox services may not start, but one common one, is if you have changed your /etc/hostname or /etc/hosts and don't have a valid FQDN (eg. proxmox01 instead proxmox01.com).
Failed to start The Proxmox VE cluster filesystem.
Failed to start Proxmox VE firewall.
Failed to start PVE Status Daemon.
Failed to start Proxmox VE scheduler.
Failed to start PVE Cluster HA Resource Manager Daemon.
Failed to start PVE Local HA Resource Manager Daemon.
The above issue can cause error messages like these upon boot where nothing works. IF this happens, make sure you have the same and valid FQDN (eg. yournode01.com) in /etc/hostname and /etc/hosts