I had the same problem on my Vizio 4K Smart TV and have found a solution . For some reason my backlight had to be below 60 . I don't understand it but setting it below 60 worked . Everyone who has this problem should try this . You never know .
[post merged with already existing thread]
Thanks for the note. This type of behavior may occur if either certain settings on your TV aren't configured correctly, or if you've enabled 'auto-adjust refresh rate' on your Roku device.
- Try going to Settings>System>Advanced system settings>Advanced display settings and siable 'auto-adjust display refresh rate'. This can eliminate black flashing behavior that occurs when refresh rates change. See more here: https://support.roku.com/article/115012823268-how-do-i-change-the-display-refresh-rate-to-match-the-...
- You will also want to review your TV's display settings related to HDR and/or 4K, if applicable. Try enabling/disabling HDR settings.
- If you are connecting to a 4K TV, you'll need to make sure you are using an HDCP 2.2 certified high speed HDMI cable for proper functionality. See more here: https://support.roku.com/article/230317588-why-is-hdcp-2-2-important-to-playing-4k-ultra-hd-or-hdr-c...
We'd also recommend reaching out to your TV manufacturer for additional help or support in reviewing or changing your TV's settings accordingly.
I have had the same issue from the day I baught the Roku. The only thing that worked was downgrading to 720. New HDMI cords, and all the setting recommendations did nothing to get rid of the black screens. I found this also happens on both my ultra and streaming stick. To make matters worse is the TV never detects a signal unless I cycle power each time I watch, unless I use 720.