Hi, I had the same issue. I fixed it by finding one corrupted image which had no preview. It shows in the list of screenshots as an empty placeholder. Be sure to look closely at all languages and screen sizes in the media browser. You'll need to delete it and re-upload the bad image. @apple there is something wonky in your upload manager that occasionally corrupts the files. It would be helpful if the error message could include the language and screen size to help isolate it. For our app we have 18 languages and 5 screen sizes per language so quite a lot to review to find the bad image.