Help Center addresses this issue:
Listing image best practices
Great listing images help you convert shoppers to buyers. Follow these recommendations to optimize your listing images:
Image orientation
The first photo in a listing should be horizontal (landscape) or square. This ensures that the center focal point of the image appears in the cropped thumbnail views.
Your first listing photo also dictates the shape of the photos that follow. Uploading the same shape photos for all listing photos will create a more cohesive browsing experience.
Image rotation
Etsy auto-rotates listing photos, but keep in mind that this depends on information included by your camera in the image file.
If your listing images are still uploading sideways, try using a photo editing service to rotate your images, or retake the photo while holding the camera in a different position. Remember that the orientation of your subject matter should match the orientation of the camera.
Listing image thumbnails
Make sure that your thumbnail images have enough of a border that they can be cropped to a square thumbnail without losing some of the product.
Our recommendations are:
- Crop your images using Etsy’s crop tool to ensure accurate framing of your item. Using an uncropped image may result in inaccuracies on the final thumbnail.
- Try to capture images of your item further back then you think you’ll need. This will give you the ability to crop in without losing parts of your item.
- Avoid square crops. Upload horizontal or landscape images.
- Use an aspect ratio of 4:3.
For more detailed information, learn about Trouble Uploading Images.
https://help.etsy.com/hc/en-us/articles/115015663347-Requirements-and-Best-Practices-for-Images-in-Y...
I'm not seeing any sideways photos in your thumbnails, and I can't look at every listing to see where they might be. Are you taking photos in portrait orientation? If so, that may be causing the problem. You should take them in landscape and crop to square instead of using portrait orientation. Etsy probably won't be making any changes to address your issue, especially since they provide a lot of information in the articles about how to fix the problem. So it would be best if you figure out a solution that works for you.
I had an issue with sideways photos years ago. I switched to landscape for taking photos and crop to square. I haven't had any rotation issues since I made that change.
