Form action triggered, but form "utter" response isn't

I’m trying to create a simple form that asks the user their name and extracts it into a slot using a form. I followed the simple guidelines for a form here.

The form action “name_form” is successfully triggered upon the intent, but then the bot simply goes to the default fallback message instead of asking the question in “utter_ask_first_name”. Why isn’t the utter_ask response being triggered?

My rule:

- rule: Get name
  steps:
  - intent: findout_personal_message
  - action: name_form
  - active_loop: name_form

The form:

forms:
   name_form:
     first_name:
        - type: from_text

The “utter” in my responses:

  utter_ask_first_name:
  - text: "What is your first name?"

This is the debugger state:

Fixed. For some reason setting the initial_value and influence_conversation variable in the slot I was using (first_name) caused the form to skip the question utterance.

The slot looked like this:

slots:
 first_name:
   type: text
   influence_conversation: true
   initial_value: "null"

But was fixed when I changed it to simply:

slots:
 first_name:
   type: text