The photo-sharing functionality in Hangouts is changing. Going forward, the ability to share photos and other multimedia in Hangouts Chat will be set by the Google Photos service rather than by the Google+ service.
What you need to know:
If Google+ is enabled in your domain, no further action is necessary. Google+ requires Google Photos so you can continue to share photos using Hangouts Chat just like you always have.
If Google+ is not enabled for your domain and you want to use the photo-sharing functionality in Hangouts Chat, you must turn on the Google Photos service in your Admin console.
This functionality change already applies to the latest version of the Hangouts app on iOS, and will take effect for web users in the next few days. On Android, if Google Photos is not enabled, users may see errors when trying to share photos until the next update to the Hangouts app, which is scheduled for the coming weeks.
Note: Google+ and Google Photos are additional services and aren’t subject to the terms of your Google Apps account agreement.