It may happen that your photos are uploaded correctly to Rentals United, but they appear upside down or rotated in the sales channels. It may be caused by wrong EXIF orientation value. Sometimes devices set the EXIF orientation value and leave applications viewing the image responsible for rotating the image. Some applications can rotate the image successfully and some cannot. That is why the photos can appear with normal orientation in Rentals United, but not in the sales channel.
You can search for EXIF viewers online and upload your photo to view the details. These applications read the metadata of your photo and display the summary for you. If you decide to use them, check specifically for the value of the ORIENTATION field. It may display text like "horizontal" or "rotate 180°. Then, you will know that this is the ORIENTATION field issue.
In order to fix this issue, you can retake your photos and upload them to Rentals United again. If you want to save time, you can search for dedicated EXIF data editors online. These applications give you a possibility to change the data in the ORIENTATION field. This may be especially useful if you do not have access to your apartment right now and cannot retake the photos or if the problem with orientation affects multiple photos. Just make sure the applications you find are safe before you use them.