Head down to your FO TODAY!!!!
Cry, beg, cajole, cry a lot more if needed, when you get there. Explain your situation to the security guards, plead, plead and plead, for them to allow you in and speak with an IO. Go with all of your documents, including documents showing you will basically loose this opportunity if your interview does not happen on or before Sept. 30th. Be prepared, they may decide to interview you on the spot. If they do not allow you in today, repeat the process tomorrow, same thing the day after. You will need to be persistent, don’t wait until your scheduled Oct. 1st appointment.