My Question or Issue
I was recently having issues downloading a playlist of offline songs from my Mac to my iPhone. I was using the latest version of the Spotify App on both.
After a lot of trial and error, and divide and conquer strategies, I realized there were multiple issues:
1) Certain songs would not sync to the phone because they had ".wav" extensions. The Spotify app on my Mac would happily play them, but they would never transfer to my phone.
2) I had a few errant files with extension names of ".mp2". I had no idea how they got there (I've been collecting these songs over the course of 20 years, so somewhere along the line I got some bunk filenames). These would play on the Spotify app on my Mac, but not transfer to the phone.
3) Some of my mp3 files had extensions of ".MP3". These would transfer to the phone, but when I tried to play them on the phone with the Spotify App, there was no sound. When I fast-forwarded to the next song or went to the previous song, the track would disappear from the playlist. After changing the extensions to ".mp3" (on my Mac's filesystem), they finally synced and played properly.
Hope this helps other people! I really wish the app would give an error message to the user!!!