I rebooted the web server to load a new kernel and it did not automatically mount the owncloud data directory which is NFS mounted from a file server.
Occasional failure to mount an NFS mount point is a bug that currently seems to exist in all of the debian based distributions. Not having the same problem with the Redhat based distributions. Not sure if it is a systemd issue or kernel issue or just what yet.
I’ve just manually mounted it, should be good now.