On suggestion, as I have dealt with similar issues from cameras and phones. All your earlier viewings are on devices that sense the photo is rotated, and they display it the right way. They display it the right way, but they do not save it that way.

By the time it reaches the internet, the internet is not set up to sense the proper direction so it displays the photo as it has been saved without making adjustments.

You need to adjust (rotate) the orientation and save it that way. That should help.