Desktop app won't load individual jpegs for me to select which ones to download

App displays iPhone photo albums, but won't display or load individual thumbnails for me to select which to download. I have transferred thousands of jpegs from iPhone 5s and iPadAir to my Mac successfully, but the latest updates have changed all of that. Now, the desktop app recognizes my iPhone and displays all of my photo albums, but when I click on my Camera Roll (for instance) it won't load the individual thumbnails for me to select which to download to my Mac. Help please!!!