Unable to Send Photos from Messages

I was sending a friend a series of photos without any trouble at all, and all of a sudden, I now only get the message "Unable to Share. There was an error while preparing to share. Please try again later." It's been happening now for nearly 24 hours, so I don't think waiting until later is the solution at all.

I've shared photos for years and have never had any trouble until now.

I have tried turning off and back on my phone; turning off iCloud for Photos and for Camera; turning off Wi-Fi and trying to send using Data; turning off Wi-Fi and turning it back on. Nothing works!

What can I do?