The iPhone could still take pictures, but the pictures never showed up on the MacBook Air. The customer resorted to emailing the photos to herself (not the easiest way to do it, but at least it worked).
Naturally I was intrigued. The iPhone’s camera worked fine. The iPhone could send and receive emails, and load web pages, and do other network-related things. The MacBook Air was on the network too, able to do email and web stuff without a problem. On top of that, the setting for Photo Stream was “On” for the iPhone, and “On” for the MacBook Air. That’s the first thing I checked, but no dice. Everything was set up perfectly. See below.
iPhone’s iCloud settings. Photos ON.
MacBook Air’s iCloud settings. Photo Stream ON.
Luckily, something on the iPhone caught my eye, and the problem solved itself. Take another look at that picture of the iPhone’s iCloud settings. Look especially at the top left of the picture. See anything there that shouldn’t be? (No.) Turns out it’s what you don’t see that is the problem.
What you don’t see is the WiFi symbol. That is the clue to solving this problem, because Photo Stream requires the iPhone to be on WiFi. Cellular data works for a whole lot of other stuff but not for Photo Stream. (Good thing too: uploading photos from the iPhone via your cellular connection– that is, without WiFi– would quickly burn through your monthly data allotment.)
It should have looked like this:
I went to General in the iPhone’s Settings app, turned on WiFi, and the photos began to sync right away. I got lucky this time– the WiFi thing was just a good guess. Next time I hear about a photos-won’t-sync problem I’ll know to look for the WiFi symbol right away, and so will you. (That’s all I have for you but you can read more about Photo Stream and its requirements in this Apple support document.)
Lesson: Photo Stream requires WiFi.
File that away.
Update: iCloud Photo Library requires WiFi too. You should use iCloud Photo Library, even if it means spending 99 cents a month to get enough storage to do it. With iCloud Photo Library your photo albums will sync automatically across all your devices. If you’re using iOS 10 you’ll see “Memories” and they will sync across your devices too. Your photos will take less room on your iPhone and iPad when you’re using iCloud Photo Library, as a bonus.