When someone sends me a photo or meme it can be viewed in messenger on my Mac Mini for a short period of time. Then the text remains and I just have an outline of a "box" where the photo was. They are viewable "forever" on my iPad.
Mac mini, macOS 14.1
I have the same problem, called Apple, on the phone for 2 1/2 hours and they couldn't resolve the problem. They told me to take it into the Apple Store. I made an appointment, the service person said his phone did the same thing and that it was a glitch by Apple and to report it. It's been a year and like you, the photos are on my phone and iPad but the gray outline remains.
Wish Apple would do something about this glitch.
Photos disappear in Messenger on my Mac Mini
