I had the same problem back about a month ago. Photos just would not load and I would see was the photo's file name. I am using FireFox and I noticed that if I right clicked on the msg thread I wanted to look at and select "open in a new tab" that 99% of the time the msgs and the photos would quickly load in that tab and several seconds later would then finish loading in first tab.... the site is loading very slowly, to the point of frustration and giving up on waiting for photos to display.
I did try all kinds of things like turning ad blockers and cookies on and off. I made sure FireFox was updated. Nothing made the photos load as fast as they had been for the past several years. Made me wonder if there is an overload issue what with users dumping 10 or more photos of the same plant.
Then one day I noticed that the photos were loading like they used to.