I don't see any option to add my local library

I am going to suggest you do two procedures.

  1. Stop PMS
  2. Next, we’ll make sure the permissions inside the PlexMediaServer shared folder didn’t get damaged somehow ( When PMS can’t save the ownership – it will ask you every time – means the Preferences.xml file can’t be written to )
  1. Lastly, we’ll claim the server using the Claim Token method to insure it gets back on your account ( Successful attachment will display your Plex username when it finishes )

(( I’m about to go offline. Let me know how you make out ))