Please tell me why my photo is rejected.

I absolutely agree with @Nancy OShea about the background!! Santa looks really ill! (He's looking green. So this isn't good if he needs to deliver presents 😞. Looking green means the person looks ill/sick.) The green background has affected Santa in that he has taken on a green cast. The composition could be better as well.

Why the hideous green background?   I don't think it does anything positive for the image.  And there's far too much of it.

Technical issues aside, unless you made the doll yourself, you may have an intellectual property (IP) problem.  Stock will probably ask for a signed property release by the artist or doll manufacturer.  If you can't provide one, Adobe Stock won't accept it for commercial use.

Read these links.

• 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/help/terminology-and-importance-of-copyright.html
• https://helpx.adobe.com/stock/contributor/help/property-release.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

You tell us the reason Adobe invoked. I'm convinced, however, that it is technical issues and the moderator had an easy job with this:

• You did a bad photoshopping job on this picture. If you photoshop a picture, the photoshopping needs to be so decent that you do not see the photoshopping:
• There is noise in the darker areas.
• The green cast does not improve the picture:
• The histogram shows strange peaks, the black in the eyes is grey. All this lets me conclude that the exposure is not correct.
• The picture is out of focus.

Review your photo at 400%. See the fringing on the right edge of the box. Also, the edges of the shadow are rough and the shadow on the left side edges seems out of place. Should there be shadows on the left?