Photo cannot be opened

Help!! I'm editing a friends wedding photos and for some reason this message keeps popping up. This is not the first time it has happened I took most of not all of these photos on my camera. If I didn't take them then I have to screenshot them to try and edit them but then the quality isn't as good. Please someone help! I've tried looking through the help desk but none of it is helpful. I've tried logging out and logging back in, making sure the app is updated, closing out all apps and going back in, and turning my phone off but nothing.
