The OJS documentation indicates that .jpg is a valid file type to upload. Files of type .DOCX and .XLSX have uploaded without problem. I have tried uploading the image files individually or as a zipped archive. Apparently the database has added a new record, but the file isn't available.
the screen shot above shows six lines with "Present file to reviewers" but no associated file name.
I'm sure there is some omission in the process on my part. There are six attempts because I have asked the author to repeat the upload process and I have logged in as the author in trying to understand the problem.