Playlist not displaying local files on iPhone

[lavellans]

I'm having an issue with local files on Spotify where it works fine syncing with my Windows laptop (finding the files, playing them, adding to a playlist etc) but when I made a playlist on my laptop with some of the local files inside, it would appear on my iPhone saying it had 4 songs inside but after clicking it my phone would say it was empty and ask me to add songs?

I have disabled the firewall on my laptop for Spotify, nothing happened. I have moved all the files to a folder on my desktop and changed the music library path to that, still no change with my iPhone. The annoying thing is that everything else about the playlist is fine (I'm able to 'download' it, apparently) but my files are just not appearing in it?

I know that many people have had a similar issue with local files in the past but I've followed all of Spotify's guidelines (same network/account, latest version of Spotify, both my laptop and apps on both fully updated) and tried the advice others have suggested on posts but nothing changed. It's just getting a little frustrating now.