why is my photo rejected

With some editing (correcting the geometry, lifting the shadows, adding some contrast), the picture would not look that bad:

The cable needs to be photoshopped as it is really disturbing, and you need to pay attention to artefacts/noise that may be amplified by lifting the shadows. It may also be that you have some noise in the blues.

If you are new to stock, you should consider these resources: https://helpx.adobe.com/stock/contributor/tutorials.html
Please read the contributor user manual for more information on Adobe stock contributions: https://helpx.adobe.com/stock/contributor/user-guide.html
See here for rejection reasons: https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
and especially quality and technical issues: https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html

And there is a distracting wire. You need to compose the picture without distractions. 

You can't see any details in the dark areas. In addition, the image is distorted in perspective.