Dialogflow followup intent not triggering on Actions on Google

Question

The setup:

My 'Default Welcome Intent' asks the user "Choose between Amsterdam, Berlin, Frankfurt, London".

Then I've created a custom followup intent. I've also created an entity called 'location', which I've added the four cities to.

My followup intent looks like this:

Here's the problem:

When I run the app in Actions on Google simulator, it always triggers the "Default Fallback Intent", and doesn't trigger the followup intent.

Here are some more screenshots of my setup, as requested in the comments:

Answer 1

The issue was me not reading the documentation properly. I've stupidly skipped the part where it explains how to accept card responses.

app.intent('Carousel - OPTION', (conv, params, option) => {
  const SELECTED_ITEM_RESPONSES = {
    'SELECTION_KEY_ONE': 'You selected the first item',
    'SELECTION_KEY_GOOGLE_HOME': 'You selected the Google Home!',
    'SELECTION_KEY_GOOGLE_PIXEL': 'You selected the Google Pixel!',
  };
  conv.ask(SELECTED_ITEM_RESPONSES[option]);
  conv.ask('Which response would you like to see next?');
});

https://developers.google.com/actions/assistant/responses