Shared photo albums
My wife has set up a shared album on her iPhone as a family member but I can't access it on my iMac (it is not appearing in my shared albums)
iMac 21.5", macOS 10.13
Have you accepted the invitation to see this album? (Subscribe to albums shared by other iCloud users in Photos on Mac - Apple Support)
Did you enable iCloud Photos in both places - in System Preferences > iCloud > Photos and in the Photos > Preferences > iCloud? Turn iCloud Photo Sharing on or off in Photos on Mac - Apple Support