Black bars on 4k clips?

Hi all,

I have uploaded 4k files (4096 x 2160) to pond5 and when they appear on the page they have black bars on top and bottom. When I open the source image on my laptop (and on several players) those bars don't exist. Why is this happening? And, will this affect the aproval of the video?

Thank you.

Probably need to define the aspect ratio properly in the edit details page for that clip.