Myidtravel will not show flights inside an hour from scheduled push. This is a known issue that is being worked out apparently. In the meantime you should be able to list for any flight the same day and a gate agent can move the listing to your current flight. If it is the last flight of the day, you can list for one the next day and they can allegedly move that too.
Sorry. This has been painful for all of us including SWA pilots.