Try connecting to a different HDMI port on your TV. Most TVs have more than one, so connect to a different port. If there is no open port, disconnect the cable from one of the other devices that is connected to an HDMI port and plug that in to your Roku.
Try a different HDMI cable. If you have a spare, give that a shot. If not, but have a cable in use with another device, try connecting to that cable, similar to listed as above.
There aren't many ways to test this. It's usually what's left after the first two. You could connect to another TV and see if the issue is there as well. If not, then the HDMI port on the Roku is good.
Unless of course there's something else entering the mix that we're not aware of. If the first three didn't yield results pointing to one of these, then more information will have to be gathered to see what this unknown thing could be.
Let us know how it goes.
DBDukes Roku Community Streaming Expert Note: I am not a Roku employee.
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