I just saw you had both config files active 
lrwxrwxrwx 1 root root 42 Jun 20 12:18 99-dietpi-nextcloud.conf -> ../conf-available/99-dietpi-nextcloud.conf
lrwxrwxrwx 1 root root 41 Jun 20 13:18 99-dietpi-owncloud.conf -> ../conf-available/99-dietpi-owncloud.conf
But this is fine in this case