Spotify only playing certain downloaded songs

[Luigipepperdot]

Plan

Premium

Country

Devices

(iPhone 5, iPhone 6s, iPhone SE)

Operating Systems

(iOS 10.33, iOS 12.3.1, Windows 8.)

My Question or Issue

I've searched online and here in the comminity but can't seem to find an answer for my exact issue.
As stated above, Spotify is only playing certain local songs which I have downloaded.
Some songs play fine, others show the message "Song Not Downloaded" "If you own the song, you can sync it from your computer".

All songs are in the same folder and this issue is the same across 3 different devices (iPhones). I have tried rebooting, downloading, re-installing. They are all on the same WIFI network.

I've tried this: https://community.spotify.com/t5/Desktop-Windows/Random-songs-albums-that-aren-t-saved-to-library-pl...

The one phone even only has spotify on it. 
Any ideas on what else I can do to fix this issue?
Thanks.