MPI_Recv not working after few iterations

MPI_Init()
// find out process ID,
// and how many processes were started
MPI_Comm_rank(MPI_COMM_WORLD, &pid);
MPI_Comm_size(MPI_COMM_WORLD, &np);
for(int i=0;i < 10; i++){
 if(pid=0){

 MPI_Send(.....) 

 // sequential code 
 }
 else{
       paralle code
   MPI_Recv(...)
}

}
MPI_Finalize();

For few iteration it's working absolutely fine but after that it sends data but it isn't received by procosses of pid !=0 . What could be a possible error?