WordPress theme got hard rejected, need advices, please help

Hi guys,
I had submitted a WordPress theme of “DNG | Responsive WordPress” and unfortunately got a hard reject (quality standard required), and them didn’t tell the reason. I hope get your help on what could be improved.

The demo is: http://demos.dnngo.net/dng-theme/

I would be very appreciate if anyone can check and give me some advices/opinions. I hope I can improve it in next time. Thanks in advance!