Wow, I'm impressed, it's a nice rendering. But the moderator will look at it with the same criteria as a photography. So, it needs to be sharp. And there should not be noise in the image. Rendering engines use noise to make the image more realistic, but in this case, it's too much.
(seen at 200%).
The good thing is that you only need to re-render with higher quality settings.
And to round-up, a little bit of reading:
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