Maps not displayed in real device

I try with google maps appli开发者_StackOverflow中文版cation in developer site. Generate api key and runs it in emulator smooth. The problem is when I deploy it in real device it shows only grid checks. I also generate release key and pasted the key in layout mapview. Whats wrong with that. Kindly help me with brief explanation.

The only thing I can think of is the data connection. Has the phone got a good reception? Does the Google Maps app work on the phone?