This seems to happen a lot . Once the BoG FP+ system gets a date stuck in its head, it won't let go of it, no matter what changes you may have made to the reservation dates. It's still associating your email with the November reservation, even though you cancelled it. Something that seems to have worked for others is to go to the Disney website and create a new account using a brand new email address that you're sure has never been used in conjunction with anything Disney, and associate that email with your September trip. Then go to the BoG FP+ site and use the new email and the September reservation number. (It wouldn't have let you make a FP+ for November. It would have happily shown you the dates and said that there are no times available for those dates. Helpful, right?)