Can anyone shed light on why didn't get approved

One glance at the histogram easily confirms the problem here. Overexposure, and an unrecoverable blownout spot. Perhaps you didn't attempt to edit your image before submission? Virtually all images require at least minimal editing prior to submission. If you're not already proficient at using image editing programs, you will need to acquire that skill set in order to be successful at stock sales.

Hello,

This part of the picture is a big problem ☹

It won't pass...

Read these guides as well - it's quite helpful:

Exposure:
https://www.adobe.com/creativecloud/photography/discover/exposure-in-photography.html

Composition:
https://www.adobe.com/creativecloud/photography/discover/photo-composition.html