iphone won't sync with itunes

Perhaps you have your Sync options set to Sync Selected playlist, artist, albums and genres, in which case you need to add the new playlists to your list of items to be synchronised with the phone.

Connect your phone to your iTunes Library and click on the phone icon that appears at the top of iTunes window:

That will display the Device/Settings/Summary pane.

• switch to the Device/Settings/Music pane (1.) - see screenshot below:

• I assume that Sync Music (2.) is already selected (there's a tick (checkmark) in the box)
• if Selected playlists, artists, albums and genres (3.) is already selected, then the sections numbered 4. will be displayed. You need to select your new playlists from the Playlists section and then tap the Apply (or Sync) button in the lower right corner of the iTunes window (not shown in the screenshot)