Your logo watermark wasn't on the image you sent them, right? If so, that's why.
The photo is also a bit small, but I assume that you just didn't upload the full version here.
Otherwise, I like the photo, but there are a few issues.
The shadows are too dark. There is no detail - it's a bit too "crushed".
The coffee beans look sharp, but the cup - especially the coffee inside it doesn't seem to be quite in focus.
I think the overly dark shadows are the reason it would be rejected. It's a fairly nice image otherwise.
thanks for your comment. It's right that i sent this photo withour a watermark.
Now when you say the Cup and the coffee are not sharp, i see it too. Although the darkness in the shadows.
Therefore many thanks.