Q: My mac is not allowing me to add music manually to my iPhone

https://discussions.apple.com/thread/7163823 - If you have signed up for Apple Music or iTunes Match you won't have the option to manually manage or sync music to a device in iTunes. Music syncing is done through iCloud and all your eligible music should appear there. Movies can still be synced.

A bit more about this, and some options- https://discussions.apple.com/thread/7194995 and: Move content from iTunes on your computer to your iPhone, iPad, or iPod touch

- https://support.apple.com/en-us/HT201593

and a workaround - https://discussions.apple.com/message/28842873#28842873

If you have not signed up for one of the iCloud based services:

https://discussions.apple.com/message/28481661#28481661 - "Music syncing has changed in iTunes 12.2.0 and iOS 8.4 Music App."

Hi,

Do you use Apple Music or iTunes Match? If so, you can't manually manage music on your phone.

Jim

If you're using the Apple Music service then on your phone go to Settings - Music and turn on "Show Apple Music" and "iCloud Music Library" If you also have iCloud Music Library enabled on your Mac then you should see all the same music on your Mac and iPhone. You can then choose to make any of the songs available offline on your iPhone. I created a playlist an put all the music in there that I want downloaded on my iPhone and then I just make that playlist available offline on my iPhone.

Did you check that you have the latest version of iTunes? Additionally, make sure that "Sync" is checked under your phone's settings.

I went into settings-Music-turned off show apple music and icloud music library. I had to eject my iphone 1st and plugged it back in. I was finally able to drag from my computer library to my iphone. I felt like an idiot because I had support help with this very same thing almost 2 months ago lol.