iTunes/Apple Music on Windows music won't sync to iPhone

I've been using iTunes on my Windows laptop. I update my music playlist, but it will not sync with my phone. I uninstall iTunes and install Apple Music on my laptop. Again, does not sync with my phone. Uninstall and reinstalled iTunes. No change. So, I decided to turn off 'Sync Library' and turn it on to see if it will sync with the laptop. Now it's taking forever to sync. Don't know what to do. I am using Wi-Fi and cellular at the same time. So, should I be trying sync with just Wi-Fi or just cellular?