I know that for pictures that I took with my phone, holding the phone normal up/down, all the pictures uploaded to app sideways. Then I read that you have to take the pictures sideways or landscape, then upload them.
I'm afraid it's a bit of a crop/turn job on the photos to get them the right way. You may have to go back to your original photo, edit it to the right direction and repost. That's what I did and it worked. I tend to use my laptop or a desktop for everything beyond quick replies on the phone.
It's a pain in the rear, but I tell you when I see all sideways pics (I know not what is happening in your case) in a listing, I always think - amateurs.