Go to the appointment fully prepared for the possibility of having an interview on the spot. In terms of how to talk about your case, I think you already have an idea of what to do based on how you succeeded in getting a Tier 2 agent to schedule an INFOPASS appointment for you. If you do get the opportunity to speak with the IO in charge of your case, you can request to know if your background check has cleared, and if your KCC file has been received. If they positively to both questions, ask to know what could be responsible for the delay you’re experiencing.