Plex can't see media folders when I try to add library

[tom80H]

Can you confirm the PlexMediaServer (system) user has access to your media files?

Synology FAQ - Questions, Answers, and How-To's

FAQ 19: Setting permissions to allow Plex access to media files Before beginning, it’s important to remember one key point; Plex doesn’t have any special privileges on Synology except for being able to access the Video Transcoding acceleration hardware. It cannot read any of your files unless you expressly grant permission. This is a fundamental principle of Linux (which Synology uses for DSM) Because of how Synology grants permission, access to files is broken into two different …

Make sure you don’t store any media in the server data directory. This will only mess things up.