Gateway ACK Enabled setting not working

[seant100]

When I enable ACK on the Gateway settings for a MySensors MQTT gateway, setting the ACK enabled setting to on seems to prevent any message being sent. When I enable that the resource logs show no messages being sent anymore. And the mycontroller.log file shows messages like this
2018-10-27 19:35:53,646 INFO [mc-th-pool-0] [org.mycontroller.standalone.provider.EngineAbstract:232] Seems like failed to send this message. There is no ACK received! Retried 10 time(s). MessageImpl(gatewayId=1, nodeEui=2, sensorId=SENSOR_BC, type=Stream, subType=Firmware response, ack=1, payload=220024004d032A95E1F71124EF90FF900F911F91CF91, isTxMessage=true, timestamp=1540661748086, properties=null)

[jkandasa]

@seant100 looks like your gateway/node not sending back the ack response.

[seant100]

@jkandasa Is there something I need to add to my sketches to tell it to send back ack responses?

[jkandasa]

@seant100 No, no actions required in MySensors library.

Can you enable debug and verify? refer: #473

[jpink]

Ack doesn't also work with my MyController - Embedded MQTT Broker - serial2mqtt adapter - USB - Arduino - Relay -setup. When I change switch state, I soon get following error:

And the switch state doesn't chance. It changes automatically after 30 s by automatic refresh.

Earlier setup: MyController - USB - Arduino - Relay works as expected.