?task=send Task doesn't send sms to 3rd party


I am running SMSSync v.3, on Android Kitkat.

I have enabled task features after every minute. This happens successfully and i’m capable to catch it on the server and act on it.
I respond to task with a number of sms to be sent (Just 5 sms), SMSSync receives the sms and put them in queue, i know it puts them on the queue because it responds back with queued messages (ID).
Above is the sample Response after responding to task=send, then it gives me feedback about the messages in queue, but these messages never go out.

After some time it no longer responds with queue messages, but keeps checking task without fail.

No message goes out of the phone.

And sometimes it send an sms that was sent even a day a go, just after getting the task=send response from Server.

Anyone know, what could have been the reason?

PS : Sending sms by responding to incoming sms, works like a charm.