I gave a try to nextcloud on a raspberry pi 4B I wasn’t using (I installed freedombox with the installer on an external USB SSD).
It usually works, but it happened twice that it wasn’t working, and on the nextclould page in plinth, there was an indication that it was inactivate. After disabling and re-enabling it from that page, it was working again.
Is it something that happens for others too? I wonder whether it happens after some kind of update, and the app fails to start again.