PHP Missing Code Error When Running 'api.access.deny'

I encounter this error when adding an Action to the login Flow. If I remove the Action from the Flow, it works again. I’d love to know where I’m going wrong, as the aforementioned line in question is simply:

 

This is the Action:

As today is a weekday (Monday), I want to deny access to the application AuthPHP for testing purposes.

The login Flow looks like this:

I followed the steps outlined in this guide.

I have changed the Action a number of times to try and pinpoint the error. It only fails when calling `api.access.deny()’, though I cannot figure out why.

Update: This issue does not occur when running the Python sample app.

Problem is not an issue as the sample app isn’t required anymore.