Some cameras don't preserve orientation information on photos. A lot of programs assume all photos should be displayed in landscape format.
Open the photo in an image manipulation program. Rotate it 90 degrees in any direction, and save the photo. Now rotate it back to the proper orientation and save it again. It should upload correctly.
I have a Windows 8.1 desktop and use the old Windows Photo Viewer for this.
__________________ May the bridges I've burned light my way.