So I cannot sync local files to my iPhone. I realized the reason is that I'm using the school's wifi which is a shared network because when I went back to my country, I was able to sync them on my private network without any problem. So, I changed the settings on my school's wifi to private network but it still didn't work. I checked whether my firewall was blocking spotify.exe but it allows it both on private and shared network. So, it technically should allow me to sync local files. I connect my iPhone to my windows desktop, I tried it even with my phone's hotspot but it still doesn't work. And there are months for me to go back to my home since I live abroad. Somebody please help me, this is so annoying.