Timeout while waiting for response from target.

I have a problem that is when i run the code on zigbee application kit(use Dynamic C) but it have an error message.
The error message is show:
「while Debugging:
Timeout while waiting for response from target.」
I’m alreay check the target is work,because i use the sample program it can be run.
what’s wrong with it?

Thanks for your reply.