This is driving me insane, and Spotify online support is not helping.
I have a Spotify Premium subscription. I want to make a playlist of some MP3 files that I own available on the Spotify Android app.
I have physical copies of the the MP3 files on my laptop, and on the SD card of my Android device. However, the Android app does not let you add local files.
So on my laptop, I have added these files to a playlist in Spotify (and also made the playlist available offline, on my laptop).
However, if I then go to Spotify on my Android device, find the playlist, and click "download", it will not download them. The files remain greyed out.
This is the case whether my phone is connected over wifi or mobile data.
What can I do?