Data bucket not populating from MQTT bucket write node

Hi all. I am receiving JSON data using MQTT and am seeing the data in the Node-Red debug window.

In the Write Bucket node, I have set the name of the data bucket. I think the issue may be with the MQTT Topic setting field. I have seen a few posts on this but am not sure exactly how to deal with it.
My input node subscribes to all topics (using: #)
Below is a pic of the debug window showing one (unexpanded) JSON packet:
How do I show all topics? Or I can just show temperature which is a field -
Are the topics the string shown as:- v3/rascalmkrwan1300@ttn/devices/arduino-lora/up : msg.payload
My device is a MkrWan 1300 (Lora). I have also used a function node to extract just the temperature.
But as I understand, the data bucket requires a JSON object.
I have done a local Node Red setup with an inject node sending JSON data to a write bucket, with a topic called data. Still nothing showing.