The saving into CSV library seems to be down. :/
I'm working on a replacement here tools.ladataviz.com.
The Voronoi Treemap will be available in February!
For me, it was having trouble grouping with a new set of data since previously the grouping had worked fined. After much trouble shooting it was having problem reading cells that were only 0 or empty (null). When replaced "0" with one, then the grouping function worked and it wasn't giving the "Error: when linking, twin is null".