SkyBox is incompatible with the programming changes we made for "SkyBox Studio V2". We have improved the workflow features for 360/VR production in our latest version of the plugin. We want to make sure our customers have the best tools to work with, to remain competitive and up-to-date.
You can still use SkyBox and SkyBox Studio V1. You just need to use the correct installer, available in your account and here:
Download the (SkyBox + SkyBox Studio V1) installer:
http://d19or1su52seym.cloudfront.net/download-files-current/mettle-skybox-studio-v1.zip