Downlink not acknowledge in TTI v3 stack

Hi Team, we have configured our end node in TTI v3 stack account. We can able to receive the uplink in TTI. Also we can able to get the data to our application server by HTTP integration. We are giving the downlink from application server to TTI. The downlink happening in TTI console side, but its not acknowledge. Even we had given the downlink from MQTT also. But same problem happening.
Kindly support for this. Thanks in advance.

What do you mean?

Position a node where its only choice is a gateway you control and watch the logs of the gateway to see if it transmits a packet of appropriate length. If it does, the problem is with the node.

You probably want to setup serial debug output and logging on your node.