Trouble with double NAT

Hi folks, 

I have a topology with 2 devices running NAT shown below

the PC is double NAT before outgoing to the INTERNET. 
After that, the PC can not access a Web server on the Internet. I have ping test IP's Web Server and DNS 8.8.8.8, it works. Then, testing packet capture via Wireshark, the result does not see any DNS response from DNS server (only see DNS query from PC)

Can anyone explain the reason for the case above?

Regards, 
Hoang Nguyen Huy