Using on add-on domain instead of primary

Is there a setting or something that I need to change to be able to use the plugin on an add-on domain in the hosting account instead of the primary domain?  Everything works fine when using the plugin on the primary domain, but I would like to switch it to an add-on domain in the same hosting account but when I try it there it doesn't pull the category list and I get "Curl exec failed: Connection timed out after 10000 milliseconds errno: 28..." in the log. I tested it in a couple of hosting accounts and the same thing happened in each one. Awesome plugin!!!