my submissions have been rejected due to technical issues, but with no detail as to why...when I upload, the preview thumbnails are blurry, and presented vertically.
Please share 1-3 pictures (originals not previews) so the experts here may offer ideas to help you work towards Adobe's world-class commercial requirements.
when I upload, the preview thumbnails are blurry, and presented vertically.
You didn't upload images straight from your phone/camera did you? Even the best photographs require some post editing in Photoshop / Lightroom before they are submitted.
To give better answers, we would need to see the actual images you submitted, not the preview thumbnails.