You are somehow locked out of your server.
- Control Panel - Shared Folders - Edit the
Plexshare - Give your username R/W permission
- Stop PMS in Package Center
- Open File Station
- Plex share -> Library -> Application Support - Plex Media Server
- Delete
Preferences.xml - Start PMS
- Open
http://ip.addr.of.syno:32400/webagain (same as with first-time setup) - Step through the first-time setup wizard as you previously did except Do Not create any new Library sections. Skip that part
- Arrive at the Dashboard
- Settings - Server
- Check the basic settings and set them again. Some will have been lost in the soft-reset.