iMac - Won't Launch

Just downloaded Subsonic to my iMac running latest version of Yosemite. When I first tried launching it I got a message saying I needed to be running Java SE 6. So I got that downloaded and out of the way. And now after that, it flat out won't launch from Launcpad. When I click it, nothing happens. No error message. Nothing. I'm totally perplexed.