we released a new beta with a few important bugfixes.
Indigo for Revit 2.6.1a
* Mesh export now properly uses the category visibilty settings in the selected view (fixes masses)
* fixed "Model tried to use undefined mesh 'RevitMesh'." error message when no geometry exported
You can download the Indigo for Revit installer packages from here: http://www.indigorenderer.com/revit/
It is also required that you update your Indigo installation to Indigo 2.6.1, which you can get from here: viewtopic.php?f=1&t=10245