Here's how I made it unlock, eventually.

First scene in the inn:
- talk to the four persons in the front (girl, man beside girl, two customers at table)
- talk to woman at bar counter
- talk to Dr. Ink

Progress the story as per normal until you're outside the inn:
- talk to woman with shovel
- talk to the crowd, and make sure you repeatedly click "talk" until all dialogues have been exhausted

Go past the gate, solve the puzzle, and return to outside the inn:
- talk to the crowd again, and make sure you repeatedly click "talk" until all dialogues have been exhausted

Go into the Zeppelin Landing:
- talk to the two men in the scene, and make sure you repeatedly click "talk" until all dialogues have been exhausted

Return to the inn:
- ignore the woman at bar counter and the soldier on the right
- talk to the two other customers

Achievement should unlock now.

Hope this helps. Please share if you're still having issues. Cheers.