So, I haven’t used the Java paho MQTT client yet. But this should help:
The MQTT clientId = ‘my-device-id’,
The MQTT username = ‘my-access-key’,
The MQTT password = ‘my-access-secret’
Could you verify that you are using the correct MQTT options based on the feedback above? Also, could you try connecting using port 1883 to test?
If this doesn’t make any sense, let me know. I’d be happy to elaborate more.