I haven’t seen a reply yet so I’ve been trying things.
One was running the command “sudo nextcloud.occ maintenance:mode --off”
This echoes a warning that comes up in red when I type “sudo nextcloud.occ upgrade” concerning updatenotification. I now see this message when I go to the web interface:
“The files of the app (updatenotification) were not replaced correctly. Make sure it is a version compatible with the server.”
I have no idea what I ought to be doing at this point.