Playlist files can be stored in any of the folders that Serviio uses for media. So if you didn't place them in a Serviio shared folder location Serviio can't see them. If doesn't matter which of the folders the playlist files are in, but I made a folder specifically for them, just to keep them all together.
Now, playlists do not appear under Titles, Movies, Folders, or any of the other presentation displays that Serviio offers. They only appear under the Playlists presentation. So first go into your Serviio console, click the Presentation tab, and ensure Playlists is set on Display Category. Click the save button, and then go back to your player and go to the main Serviio view. Playlists should be one of the selections.
If you've done all that and still nothing appears, then the format of the playlist file might have issues. In my playlists, I use the absolute path to the video file:
File3=G:\Movies_E\007\Goldfinger (1964).m2ts
This is in the PLS file format, but in M3U format the path is the same. Playlist Creator has options on how to specify the path, and with multiple file locations it's best to use absolute.
Dan
LG NANO85 4K TV, Samsung JU7100 4K TV, Sony BDP-S3500, Sharp 4K Roku TV, Insignia Roku TV, Roku Ultra, Premiere and Stick, Nvidia Shield, Yamaha RX-V583 AVR.
Primary server: Intel i5-6400, 16 gig ram, Windows 10 Pro, 22 TB hard drive space | Test server Windows 10 Pro, AMD Phenom II X4 965, 8 gig ram
HOWTO: Enable debug logging HOWTO: Identify media file contents