message delivery report ,Process message not getting called

Hello everyone ,

I'm developing chat application in android.

For message delivery report, I have attached DeliveryReceiptRequest.addTo(message); to very message i send and i get receipt response in process message method of ChatStateListener but sometimes even after receiving delivery report my processMessage() method does not get called. and at the same time chat with other user deleivery report works fine.

What could be reason .

Thanks in advance.