Roku Ultra Losing Connection to TV every few minutes

Our Roku Ultra (circa 2020) has recently started to lose connection, the screen going black and then coming back on (audio 1st, then picuture) to whatever app we are watching. I thought maybe the Roku had reached its end of life and purchased a new Ultra today, but the issue continues. Now, every 2-3 minutes the screen goes black, and I get a message "No Signal, check the external input or select another input using the INPUT button." This is a new HDMI cable and Roku Ultra as of today. Our system includes a Denon hub for surround sound. Any suggestions are welcome.