Help request: Messages on Mac won't send photos

My wife has an odd problem on her MacBook Air (M2) running MacOS Sequoia 15.7.1: She can’t send photos (JPEG), either from Photos by pressing the + or by dragging and dropping them from her drive into Messages. Neither works. The photos appear on Messages in her computer, and it appears that they have been sent, but recipients just see a blank bubble.

On my M2 MacBook Pro running 15.7.3, I can do this with no problem.

She can send them from her phone. It’s driving her nuts because she prefers to download photos to her Mac, edit them, and then send them to friends/family.

Has anyone else run into this problem, and if so, any suggestions for a solution? We’ll try upgrading to 15.7.3 as soon as we get back from a trip, but I think the problem has been around for a while.

Thanks for your time and trouble! And happy holidays to those who are celebrating.

Edited to add: at first I thought it was just drag-and-drop, but it won’t send photos from Photos either.

Is it just edited photos that have the issue? If so, maybe the photo editor is the problem.

Can you view the photos in question on your Mac (by Airdrop, not Messages)?

Is the filename correct - maybe it shows .JPG but is another format.

Hi Michael - thanks for your reply. Images are in the correct format, and I can see them on my Mac. My wife can upload them to Facebook, email them, send them in Insta, Messenger, etc. – just can’t drag and drop them into Messages. She sees them in Messages, but the recipient just sees those small blank bubbles. It doesn’t matter whether they are edited or unedited.

I think we’ll install the latest version of Sequoia. If that doesn’t fix it, I’ll try deleting Messages preferences. I might also ask my BIL, who’s an Apple engineer (though Messages isn’t his area).