I’ve tried Down Cemetery Road on my server and it shows instantly.
Check access permissions Synology FAQ - Questions, Answers, and How-To's - #12 by ChuckPa
folder structure https://support.plex.tv/articles/naming-and-organizing-your-tv-show-files/
and file names.
Keep in mind that you never add individual tv shows to a plex library, but only point the library to the folder which holds all your tv shows.
