iMessage won’t load pictures? Only loads as a j.peg

this happens a lot where someone will send me a photo, or multiple and I can view them just fine as soon as they send them to me. But the next day I can only see them as “j.peg” attachments that cannot be opened or even forwarded. I have my MMS on, my “keep forever” on messages, I have restarted my phone, I have logged out of my iCloud and back in, and I have reset my network and reconnected. Nothing has worked. It doesn’t just happen with one person. And it’s usually when I get images from people who don’t own IPhones but I’m able to see the images just fine once they first send them.