Quite sure it’s configured correctly. When I enter the url of a gallery on a different host, it simply won’t load. And neither will the settings page. I’ve tried using a separate hosting space of mine as the “remote gallery” as well as giving it the url of my own machine’s web server which should have eliminated any major speed issues. All 3 server locations work properly when I enter a REST url for that server’s gallery into a wordpress installation on the same server.