Music on my iPhone

I have a lot of music on my hard drive which I’ve arranged into folders (with each folder containing albums/playlists) and everything is in my Apple Music app on my Mac. Earlier, this app used to be called iTunes and everything was there too. I could simply connect my iPhone and sync all my music in order to play tracks later off the device (phone) even without an internet connection. This is why I’ve always purchased an iPhone with maximum storage - I’m a little outdated now and have the 128 Gb iPhone 6s Plus.

I’m not subscribed to Apple Music or iTunes Match although I have purchased and pay each month for 200 Gb iCloud storage.

I’m trying to download all my music to my phone the way I used to earlier but weirdly enough although some playlists are showing up, they are mostly empty and the rest aren’t showing up at all.

Does anyone have a solution?

Thanks all

Tony