Image rejected because of technical issues

Hello,

You have a very bright white patch on the leaf- so this means it is 'burnt out'. There is no detail here.

Secondly, think about your composition, it's not so well composed.

Thirdly your white balance needs to be altered a bit - that is, your colour temperature. The image is a bit too yellow, which makes it too warm, so you have to decrease it, by adding a bit more blue. However, this is easier done if taken in raw. 

The focus is rather soft as well.

Have a read if this from Adobe. It is a brief guide on what they expect.

https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html