Suggestion: Since this is a new installation, so no history, etc to save, completely remove Plex Media Server from the system, reboot the NAS, then start from scratch with a manual installation using the latest version downloaded from Plex.
FAQ 9: Uninstalling PMS - Completely start over
- Package Center - Remove the Plex package
- Control Panel → Users - Delete user Plex
- Control Panel → Shared Folders - Delete the Plex share
- Restart DSM
