Lately when someone sends me a picture via iMessage, I see a box that says "Tap to Download" instead of an image. Most of the time when I try tapping the box, it says "Downloading" but it is stuck at 0 bytes out of about 2 MB. Other times it will actually download after I tap it and show me the image.
This seems to be tied to the user sending me the message. E.g. I can view all photos I get from Alice perfectly (no tap to download required), I can view all photos from Bob (after tapping to download), I cannot view any photos from Charlie (I get a tap to download box, but it's stuck at 0 bytes).
If I view the conversation on another device (e.g. a MacBook), I see the image just fine.
Why is this happening, and what can I do to resolve this issue on my iPhone?
I tried restarting my phone, but that doesn't help.