Some users have had success using an HDMI converter, while others have your experience. It seems sensitive to the specific converter, but I have no idea what ones might work.
First suggestion is of course ensure you've selected the correct input on your TV. Next, some converters have some sort of switching to change some internal settings that might change compatibility.
You might connect the Roku to a TV with an HDMI input and manually set the resolution to 720p, and then try again on the converter. Perhaps the converter isn't handling 1080p correctly but 720p might work.
Dan
Roku Community Streaming Expert
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