The best I can give you is "Keep trying!" Also, always check back about 15 minutes later. Many people use multiple computers or windows, or even multiple family members, that all try to grab a site at the reservation window opening time. If they hit on more than one, the system holds all of them for 15 minutes while they complete the registration on the one they want. The others are then released back into the available pool when the hold expires. We've gotten in several popular Florida and other state parks on the "rebound" over the years. We've also found over the years, that we really like some of the smaller lesser known Florida state parks that are usually easier to get in to.