@Peruffo, Riccardo We had internal discussion with our product team and they suggested that this might be related to Enable MQTT setting (for MQTT capabilities). Can you enable this setting before creating the event subscription and then validate?
Imp Note: Once MQTT is enabled, it cannot be disabled.
Our product team is working on a fix to provide meaningful error message (like MQTT needs to be enabled) and appreciate the feedback. I hope this helps and let us know if you still face the issue or any other questions.
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