I'd be happy to take a closer look to see how we can help.
Is there a light showing on your device? How are you powering the device? Is it plugged into the TV USB port, or is it plugged into the wall outlet with the provided cables? In addition, have you tried using another HDMI port on your TV as well as trying your device on another TV to see if you are seeing the same issue?
Have same issue. Plugged into wall outlet not tv. Swapped with another Roku that.is working on another tv and same problem. Moved that working one to the same cables where this started and it works fine with those same cables. I think I have all Roku express models. Don't think I can get to settings to get the serial number