Exposure, focus and other issues.
Read these guides.
also IP issues with the phone. Samsung Bixby.
There's also a big spot on the front of the phone, which was possibly caused by dirt on your lens....
Actually, its not. Checked before and after that photo.
Regardless of the reason for the spot, it could quite possibly be another reason for rejection.
Before you submit anything to Stock, compare yours with current inventory.
https://stock.adobe.com/search?k=hands holding phone
1. Does Stock already have millions & millions of these? If yes, don't submit it. You won't make many sales.
2. Is yours as good or better than what Stock has or does it need improving?
3. Examine your best images at 100-300% magnification in Photoshop or similar image editor. Correct images if you can, otherwise discard them.
4. Submit 5-10 of your best corrected images to Stock -- highest visual & technical quality, proper exposure, good focus, sharp details, pleasing composition. Sit back & wait for review.