pilot2atc is normal for clearance and pushback until taxi to rwy for take off , atc assign me to tower freq and when request for departure atc no longer respond..til the whole flight pls help..

You may be using incorrect phrases.  If you email the P2A Log file to me at [email protected], I will see if I can spot the problem.

P2A Log files are located in: C:\Users\<UserName>\AppData\Roaming\P2A_200\Logs where <UserName> is your PC user name. 
Portions of the path may be hidden by default, so be sure Windows Explorer has Show Hidden Items checked in the View tab.
Dave