Why am i not getting GCM push token in test environment

I am trying to test my application in test environment. GCM not able to register the device and returning blank token ID. But it is working properly in Production environment (getting token ID). I am using the same code and pointing to different environments.

What might be the cause? Is there anything that we need to do with server side?

Please help in solving this issue, i have been working on it from past two days.

Thanks in advance.