iTunes won’t let me download purchased music to new iPhone

Hello alxkrann.

Thanks for reaching out to Apple Support Communities. We understand that you are having some trouble with downloading previously purchased music for your new iPhone 12. Congratulations on your new iPhone. We will be glad to assist.

Please see the following resources:

Hide and unhide music, movies, TV shows, audiobooks, and books

Redownload music

If music, movies, or TV shows from the iTunes Store, Apple Music app, or Apple TV app stop downloading

"If you still can't restart your downloads, try these steps

• Restart your iPhone, iPad, iPod touch, or computer.
• Make sure that your iPhone or iPod touch is updated to the latest version of iOS, iPad is updated to the latest version of iPadOS, or Mac is updated to the latest version of macOS. On your PC, make sure that you're using the latest version of iTunes for Windows.
• If you use Wi-Fi for Internet access, use a different Wi-Fi network when you download. If you connect to a home network, restart your Wi-Fi router. Also, check for and install any firmware updates for your Wi-Fi router. Refer to your router manufacturer's website for information on how to update its firmware.
• If you can't connect to the iTunes Store, check your settings and network connections.

"

Cheers.