The end of Apple Photo Stream
Recently, Apple sent out an email stating that on July 26th they will be shutting down the "My Photo Stream" service”. This free service has been available since the release of iCloud in 2011. Photo Stream allowed us to upload the last 30 days' worth of up to 1000 images and videos for free, and share them with other iCloud accounts.
Check if you will be affected
iPhone, iPad, or iPod touch
Go to Settings > iCloud settings (your name) > iCloud > Photos. If you don't see the Photo Stream option or if it's turned off, you are done and have nothing to worry about.
macOS
Open the Photos app, then choose Photos > Preferences. Click on iCloud (or Photo Stream). If you don't see the Photo Stream option or if its disabled, you are done.
What to do if you are using Photo Stream
The easiest way on your Mac is to open the Photos application and select the "My Photo Stream" album. Select the images you want to keep and drag and drop them into the main Photos library.