I have had this issue before. You tap on a photo to open it on your iPhone or iPad and you get an error message like, “There was an error loading this photo”. I think this occurs when people are using the “Optimize Photos” setting on their iDevice. Obviously, this can be a little annoying, but there are ways to fix this issue. This article lists several things you can try to make your iPhone or iPad behave. The solutions are not too drastic, but may take a little time to implement.