I had this problem too, and have only just remembered how to solve it, while looking for a solution myself, funny how memory works.
You can only view photos from within a slideshow on the iphone. Clicking on photos and then the play button at the bottom, rather than clicking on an individual photo. You can then click through the photos or pause on a particular as you see fit.
You may want to reboot both your phone and the computer you are using to ensure that the iPhone is not in a glitch nor the computer. Once that is done, reconnect both and attempt to do again.
Answers & Comments
I had this problem too, and have only just remembered how to solve it, while looking for a solution myself, funny how memory works.
You can only view photos from within a slideshow on the iphone. Clicking on photos and then the play button at the bottom, rather than clicking on an individual photo. You can then click through the photos or pause on a particular as you see fit.
You may want to reboot both your phone and the computer you are using to ensure that the iPhone is not in a glitch nor the computer. Once that is done, reconnect both and attempt to do again.