[Plugin: W3TC] Grey CDN options

Hi all, I’ve just migrated servers and am having an issue setting up the CDN on W3 Total Cache. In General Settings when I view the list of supported CDNs I am finding that Rackspace Cloud Files is grey and unselectable. I am not given any information as to why and the rest of the plugin operates without a hitch. Any help in resolving this issue is appreciated.