Unable to trigger the 'storage.onChanged' event

Add-ons Development
#1

I have followed what was done in the demo:

browser.storage.onChanged.addListener(storageUpdated);

function storageUpdated(changes, area){  
  console.log("been here");
}
#2

Missing storage permission? I can’t think of anything else.

#3

I have storage permissions.

I had an issue with promises, was expecting the event before the data was actually changed. I then added the console output but tbh I don’t remember why it was not firing as supposed, I did too many changes to track this.