Synced music files won't play on iPhone

I have a lot of personal music and playlists so it takes a long time - hours and hours - for iTunes on my Windows laptop to sync to my iPhone 13Pro (1tb). After multiple sync sessions of the last two days I checked my phone and it shows most all of the music files as existing there, on my phone. Except, it won't play any of them. There is the presence of a grey circle with a down arrow (a download icon) and the three white dots next to it. The status bar at the bottom just says Loading...

For what it matters I don't want Apple Music and don't subscribe to it, I want all my music to exist on my phone's 1tb drive and play directly from it. Nothing is worse than driving through an area with poor cell service and not being able to play a song - that I own - because it cannot download.