I can get roku to come up on TV screen and all the channel's are there, when I click on one to play ,it comes on briefly but no sound and the screen goes black, if I click ok it comes back up you can tell it is playing by the time bar, but screen goes black again. can't figure out what's going on, hate to give up on roku altogether.
Before doing the below, Restart both your Roku and your network equipment (Router, modem, extenders, etc). If still experiencing behavior, try the below to see if just a display sync/resolution issue.
If you still have the other television that your Roku device was connected to, try plugging it back into that one and make the below changes.
1. Settings/Display Type/[720p] <--manually set to 720p, do not use Auto-Detect
2. Settings/System/Advanced System Settings/Advanced System Settings/Advanced Display Settings/Auto-Adjust Display Refresh Rate/[Disable]
Then take this Roku device (as-is) and plug into your new television and see if issue persists. After testing it out and performing a System Restart (Settings/System/System restart or Settings/System/Power/System Restart), and making sure everything is working, you can try manually adjusting the Display Type to your preferred format on the new television, and then re-enable the Display Refresh Rate (this is tv-dependent. Some tvs perform better with it enabled, others need it disabled if getting too many screen flashes).
Additionally, try using another HDMI port on the new TV to see if it makes any difference. If you have a spare HDMI cable, try that as well. And make sure you are powering the Roku device from the wall outlet, not the TV USB power port. (an underpowered port is a culprit of many video related issues as well).
Feel free to post an update or if need more help/issue persists. Include Roku model number (Settings/System/About)