If you email the image to help@therpf.com I will test it out. If I am able to get it to work with the changed extension I will email the image back to you for posting.
Look at the photo on your iphone that you are trying to upload... also in the screen shot you are providing us, it clearly states the extension is a png.
I am betting you did the following.... You first took a photo with your iphone, and it was a .jpeg, but the you decided to edit it by zooming in and then taking another screen shot to have a better cropped image (by clicking the power button and bottom button at the same time), then it converts to a png. You need to just use the actual photo you initially took. I hope that makes sense, lol.
Edit:
I am not sure if what I typed made sense... so I put together this chart. It shows how you change a jpeg into a png without even realizing it.