写真が不採用になりました。どこに問題があるのでしょうか？

It's very important to review your photos at 100% - 200% magnification.  Technical issues usually become very obvious then.  As @Marianne-Deiters mentioned the depth of field is shallow and not a lot of the flower is in focus.  You also have a lot of noise and the photo seems slightly underexposed.  You might also want to straighten out the image so the pathway behind looks level.

The corrections you made removed the noise, but it also lost the detail of the photo making it look more like a painting.  I doubt if the corrected image would get accepted either.  Again, look at 100% magnification - I am including a snippet of both images at full magnification.

Take a read through the requirements and rejection reasons for stock photos again.  Aim for natural looking images, that are lightly processed.  On a side note, Adobe Stock has millions of flower photographs, so if you do get some of yours accepted, don't expect them to be big sellers for you unless they are spectacular and offer something different for the customers.  I will say though that photographing flowers is a great way to practice, improve your technique and skill.

• Submission Requirements:  https://helpx.adobe.com/stock/contributor/help/photography-illustrations.html
• Reasons for Rejection:  https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• Quick Start Guide:  https://helpx.adobe.com/stock/contributor/user-guide.html

Best of luck with your future submissions.