sync is greyed out, how to turn back on

Hello and welcome to Apple Support Communities pinto437,

It sounds like you're wanting to sync an iOS device to iTunes on your Mac but the Sync button is greyed out. being able to sync content to your devices is an important part of their function, so I'm happy to help you out with this.

First, let’s make sure you're running the most up-to-date version of iTunes, as well as the current macOS version you're running. Since iTunes and macOS are bundled together, updating your Mac will ensure iTunes is too. Here's steps on how to update: How to update the software on your Mac

Next, double-check that your Mac is authorized in iTunes: Authorize your computer in iTunes. When you try to sync with iTunes, use the steps listed here: Sync your iPhone, iPad, or iPod using iTunes on your computer.

Thanks for using Apple Support Communities.

Take care!

Do you have a subscription to either Apple Music or iTunes Match? If so then typically iCloud Music Library would be enabled in both iTunes and your device, and all of your library would be available to either device without syncing.

tt2