Can someone please help and tell me why my picture was rejected?

All I see is a big blob of white.  It's not suitable for use in commercial projects, sorry.

Read your Stock Contributor User Guide and compare your work with other submissions in Stock's inventory.   If you want to be successful at Stock photography, avoid fiercely competitve keyword categories like flowers, plants, pets and pictures of the sun.  There's too much of that already. 

• https://helpx.adobe.com/stock/contributor/help/reasons-for-content-rejection.html
• https://helpx.adobe.com/stock/contributor/help/quality-and-technical-issues.html
• https://helpx.adobe.com/stock/contributor/user-guide.html/stock/contributor/help/photography-illustrations.ug.html
• https://helpx.adobe.com/stock/how-to/tips-stock-image-acceptance.html

Better luck next time. 🙂

Technical issues? Adobe did give you a generic reason.- You should forward that. Then, as a matter of practical issue: don't check all the topics available. Getting critique for an asset is contributor critique. You should check only that in that case.

Now the picture:

It's clearly overexposed, as shown on the histogram:

Blacks (left) are missing. It's clear, that the sun is blown out and only represents a white circle. You can't change that if you shoot directly into the sun. However, you need a focus point, and that can be only the plant in the foreground. In your picture, the plant is out of focus. And as @RALPH_L correctly states, not enough of the plant is in the picture. In addition, you have colour noise in the darker areas.

First of all, what is the subject? There is not enough of the flower showing.

The sun is overexposed so that no details can be seen. When printed, this makes a large white dot.

The shadow area is underexposed and noisy.

Because you shot into the light, the dark edges around the plant show a purple halo (chromatic abberation).