Local files on phone

[AK2]

Plan

Premium

Country

Device

Operating System

 Android 

My Question or Issue

I know this has been discussed before but I've tried everything suggested and it still doesn't work.

I want to make a playlist using both local files from my computer and streamed songs from Spotify. I switched to premium specifically for this purpose. I need to be able to play the playlist from my phone. 

I updated Spotify on both devices. I made sure the files were mp3. I moved them to a new folder. I'm using the same WiFi.

The songs play fine on my computer but are gray on my phone even after downloading. This is very frustrating. I don't know what else to try.