Cannot sync photos "iPhoto library is not yet available"

When syncing iPhone 5s to iMac running Yosemite and get the following error:

"iTunes cannot sync photos to the iPhone "iPhone" because your iPhoto library is not yet available. Please try again later."

This phone has been syncing with iPhoto for some time now. This is a new one to me.

Tried rebooting the phone and the desktop machine, same result.

Interestingly, in iTunes when selecting the "photos" page all I get is the spinning circle for the iPhone, the other selections, Summary, Apps, etc., all load fine.

The same situation is true for the iPad mini, the photo page never loads. I have not attempted to sync the iPad since this error appeared.

Anyone familiar with this error?

This mac has had the "iPod" cache folder deleted in past months to clear another sync error, but had been syncing fine since then.

iTunes version 12.1.050

Thanks!

Cross posted following no replies on iTunes community.