Hello,
does some body is familiar with the softaculous ScriptInstaller?
unfortunally the script only allows upgrades the newest version.
eg.: Upgrade from 28.0.9 is only allowed to 30.0.0.
This is especially relevant because nextcloud has several officially supported revisions.
Furthermore, it is strongly recommended by nextcloud to upgrade first to last version of major-release and then update to latest release without skipping any major version.
This means Update has to be preceded as fellow:
28.0.9 → 28.0.11 → 29.0.8 → 30.0.0