This incident has been resolved.

While the Land Store maintenance continues, it's still possible to get new regions via a support ticket under Land & Region > Order Private Region. We're working on getting things back to normal, and apologize for the delays.

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.