Unfortunately, you must be able to first get the date that is exactly 7 months out from date of arrival before you can reserve any days afterward. Thus if you choose to waitlist you can reserve none of the days.
Your situation has happened to many others and not just with GCV. It is likely that what is happening is that there are only one or a couple rooms opening any given day and who gets them really depends on how fast your computer communicates with Disney's computer in comparison to many others who are hitting that reserve button at 8 a.m. eastern. Others think it is just a glitch in the system and a reservation already made the day before for that day, perhaps by someone whose start date is earlier and is walking a reservation, just does not show up until the system opens in the morning. Either way, you are being blocked out.