Please make sure that PlaylistSync has permission to read your media storage. Also, some music players use their own playlists systems instead of the default one from Android, so PlaylistSync won't support them.
Incompatible: Poweramp, RealPlayer...
Partially compatible: Samsung Music and Google Play Music.
Compatible: PlayerPro, Rocket Player, jetAudio...
For more help, please checkout the "Not seeing your latest playlists?" button in the Backup tab.