MQTT Transmission Connection Lost Error

I am trying to setup Ignition MQTT Transmission to the AWS IoT Endpoint server with certificates and keys.
I have followed the instruction as per the below link: []
I have checked that AWS IoT certificates and keys are working fine but still MQTT Transmission is not able to connect AWS IoT Endpoint server. Please assist and let me know if you need any further information.

Getting below error in the Ignition log:

TahuClient 14Mar2024 22:06:57 ME-a2026340-4cb3-433c: connect with retry failed due to Connection lost

org.eclipse.paho.client.mqttv3.MqttException: Connection lost


at java.base/ Source)

Caused by: null

at java.base/ Source)

at java.base/ Source)

at org.eclipse.paho.client.mqttv3.internal.wire.MqttInputStream.readMqttWireMessage(


... 1 common frames omitted

That almost certainly means some firewall along the network path is killing the connection. Possibly using a deep packet inspection that doesn't like MQTT.

Also, be aware the AWS IoT broker has a limit on message size. If Transmission publishes a birth with a large tag map that exceeds this limit, IoT Core will drop the connection.

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This error message also appears for a very simple issue: wrong password. It was my case when testing with highbyte broker.