What troubleshooting steps have you taken so far to try to resolve the issue? 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?
With more information, we will be able to assist you further.
Mary is asking whether Roku is plugged into a USB port on your television because the ports on many televisions only supply 0.5 amp or less, which is not enough to power a Roku reliably.
It is recommended that you power your Roku device via the power adapter that came with it, plugged into your house power. If you no longer have the USB power adapter that came with your device, you may have another one handy from another device that can be used -- just make sure the tiny print on it confirms it has a 5 volt dc output of at least 1 amp.
Roku Streaming Stick +, 3810X, Ser YH0059427035, wifi - Samsung UN55ES6100
Roku Streaming Stick, 3600X, Ser 5S56D8240827, wifi - JVC EM37T