I have a brand new Roku premier. Plugged it into my Samsung 65" 4k Ultra HD TV (tv is roughly a year and a half old) and it let me set up my new account, but now when I have the Roku open it spends 95% of it's time with a black screen on the TV. The other 5% of the time, the Roku home screen will flash onto the screen, but it's so fast, you cant even read anything on it, then it immediately flashes back to a black screen. I've switched cables with known working devices, so I don't think it's that.
