@cshen, try another input on the TV, another HDMI cable, or another TV entirely. If none of those help. find the reset button on the bottom and with the power connected press and hold the button for no less than 30 seconds regardless of what's happening onscreen.
Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution."
If you appreciate my answer, maybe give me a Kudo.
I am not a Roku employee.