Can't sync iPhone 6 iTunes library with PC iTunes library

I have an iPhone 6 running iOS 11.2.6 and iTunes v12.7.3.46 installed on my PC. I have all my music saved on my PC, which I transferred from an old PC. I also updated my iTunes ID when I changed my name. Now, I can only see my music saved on my new PC on my iPhone 6 if I enable Home Sharing, despite syncing my device while plugged in. I want to have my music on my iPhone without using Home Sharing - how do I do this? (I didn't have any issues syncing the library with my older iPod nano).