This is because purify.min.js is not present so it cannot load it. This can be seen under sources in DevTools so I guess that node-red install package is not installing this. But will this account for no output in the debug window
Note The broker is on Raspberry Pi and I have tested this and it works both using the Pi to publish and subscribe and to an ESP8266 to turn on and off an LED.
Any thoughts ideas on how to solve this or I will have to ditch Node-Red unless I have more success on my Mac.
Tell us more about the actual problem you are seeing. Where are you seeing nothing in the debug node? If you are subscribing to an MQTT topic then install MQTT Explorer which many consider an indispensable tool if you are using MQTT. Then you can check that there is actually something to subscribe to on the topic.
OK on ignoring that issue. What I am seeing is that when I run the example as per the video tutorial when I inject the message I get the pop up "Successfully injected sensor 1" but the debug panel on the right remains empty.
In this example node-red is the publisher and the subscriber hence the debug node (or that is what I assume) and the video shows.
Many thanks it works now and new'ish i.e. very much a novice and since I copied the video tutorial I assumed that the # was acting like a wild card. However I have also just noticed the extra s in sensors/#