I would call member services tomorrow and have them double check those dates for you. The online site has been having a lot of problems and a lot of error message keep coming up. They can check inventory to be sure. But it is a nice time to go.
You are trying to book four months out. It is very common for any time of year, including any DVC slow time of year which includes early March, to have difficulty getting anything for more than a night, other than possibly SSR, OKW, or AKV, at four months out and many times those are even iffy.