Thanks. I hadn't realised that the custom mqtt messages also removed the /<serial>/ part of the topic. All working now.
Hi toe0321, thanks for asking.
Yes, you can. There is a way to specify custom topics when using MQTT_CUSTOM please see the CONFIG section in the documentation. It is available in the latest FW 2.2 version, if you don't have it, you should be able to upgrade it from the local configuration panel.