iTunes cannot sync photos to the iPhone “iPhone SE” because your Photos Library is not yet available. Please try again later.

Getting "iTunes cannot sync photos to the iPhone “iPhone SE” because your Photos Library is not yet available. Please try again later." when I sync my iPhone to my iMac. This was happening with my previous iPhones and is now happening with my new SE. Only have Favorites (pics) set to Sync. Someone suggested leaving the Photos app open for 24 hours before syncing, which may have worked once. I don't remember. But it's not working now. Favorite pics were syncing before and I have some of them on my iPhone but it's not updating. I have 325 pic marked as Favorites in Photos on my iMac but only about 35 are synced to my phone right now.

Photos Version 1.5 (370.42.0)

iTunes 12.3.3.17

iPhone SE 64Gb iOS 9.3.1

iMac 27" late 2013(?)

3.2 GHz Intel Core i5

8 GB 1600 MHz DDR3

OS X El Capitan V:10.11.4 (15E65)