Plex Documentation → Your Media → Naming & Organizing Your TV Show Files
You must follow Plex naming and organization guidelines (ep1.mp4 does not do so).
Read the linked guide and rename your folders & files appropriately.
This post has additional information: Plex only recognises 1 episode - #7 by FordGuy61
Write back if you run into difficulties. Include the directory path and file names with extension (directory listing, screenshot, etc.).
