Hello, Your screen going blank is either caused by the TV the HDMI cable or the Roku itself.
Follow these steps to fix the issue:
1) Shut the TV off and unplug the Roku from power (pull the power cord out of the back of the unit).
2) Unplug and reconnect the HDMI cable on BOTH ends making sure it's secure.
3) Plug the Roku back in and turn the TV on.
Let me know if you do or do not see the Roku letters bouncing on the screen.
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