Was finding this difficult to trace cause but hopfully this might help others
proxmox (PVE1@ 192.168.1.2/24) (working fine for several months)
VM Zentyal 6.3 VM (192.168.1.1/24)
VM CenOS etc
Client (PC@ 192.168.1.116/32 DHCP via Zentyal, Zentyal wont allow /24 not...
Failed to try-reload-or-restart spiceproxy.service: Unit spiceproxy.service is masked.
dpkg: error processing package pve-manager (--configure):
installed pve-manager package post-installation script subprocess returned error exit status 1
Errors were encountered while processing: