photos not showing up on imess

What do you mean by A lot has to do with the sender's use MMS versus SMS. Apple's iMessage only supports one standard on the computer?

I have the same problem on a new MacBook Pro. I tried signing out and back into iMessage, restarting my Mac, and even verifying that I had MMS enabled on my iPhone, low quality mode is off, but nothing seems to be working. It is not just the pictures that are being sent to me, but also the ones I have sent from my own iPhone that are not showing up on my Mac. I am using macOS 11.4. And to add to the problem some pictures will show up, but most will not show up.

A lot has to do with the sender's use MMS versus SMS. Apple's iMessage only supports one standard on the computer.