why my image is not accepted ?

In my opinion, the flecked green background is unsuitable for vector graphic use.  I would not buy it.  I prefer to buy vectors on a plain white background so I can use the graphic in commercial projects. 

Also as @Jill_C said, watermarks, signatures and date & time stamps are not allowed on submitted artwork.

Read the DOs & DON'Ts in your Stock Contributor's Guide for more details.

• 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

Without evaluating the quality of the drawing, the obvious problem is the inclusion of your watermark.