Hello, Help arrive!
If you are experiencing:
A. Grey title in Playlist
B. Cannot play mp3/m4a on iPhone
Please make sure the songs import into Spotify:
a. Not protected by DRM
b.In supported format (https://support.spotify.com/us/using_spotify/features/listen-to-local-files/)
1.Make sure your computer and mobile devices (iPhone) in the same WiFi network.
2.Remove the playlist which you find the problem
3.Remove and re-add the "Local Sources" - Make sure all songs synced.
3.1 Reopen Spotify app (MAC) [in case if you added too many songs] [Recommend to do]
4.Make sure all the songs which added can be played in Spotify (Mac)
5.Make whole new playlists (Recommend using different name from preventing sync error)
6.On Mac, check all the songs in playlist whether they can be played or not.
7.Download playlist on your devices(iPhone)
Please let me know if you have any questions.