It is the last dialogue in the chain. But the NPC does nothing and the door remains locked. The door tag is correct. The NPC has the key for the door. The door requires the key to unlock. I am very frustrated.
Hint: Do not copy and paste @andgalf’s version into your code. Due to a (much requested by other users of Discourse but not us) feature of these boards the double quotes will be wrong for coding purposes being of the 66 and 99 style. That is why it is essential to post code in code blocks on here. So for everyone’s convenience here is the correct version of that code -