Apple Music playlists not showing up on iPhone when adding songs from computer

I only have a few different playlists, one of them I have I'll download songs from youtube to an mp3 format and I keep them in a folder on my desktop (windows computer). When I try and add songs to that playlist straight from my computer I can't see the playlist anymore on my iPhone. The song itself will show up in my library but the playlist just vanishes from my library. I have synced libraries turned on and I'm not sure what the issue could be. I have to add the songs from my folder to Apple Music manually so I don't see how that would be an issue. I've tried looking up the issue and most of what I've seen was to make sure sync libraries is on and I know I haven't turned it off.