The Land Store will be undergoing unscheduled maintenance. We are sorry for the inconvenience!
Although the land store is unavailable, new regions are still available for purchase via a support ticket, filed under Land & Region > Order Private Region.
Please see https://community.secondlife.com/blogs/entry/4497-limited-availability-of-new-second-life-regions/
for more information and other options for finding land in SL.
It is still possible to manage your current land holdings via land.secondlife.com.