I have tried plugging the Roku Express into all three of the HDMI ports in the back of the TV, even tried using a different HDMI cord to plug into the TV and the Roku sensor, and tried pushing the reset button with a toothpick, and tried unplugging the power and plugging it back in. The Roku Express still does not send any signal to my TV on any of the HDMI channels, even tried to get to the HDMI channel via the Input button on my TV remote, still doesn't connect to the Roku. When I hit the home button or any of the buttons on the remote, I can see a little white light winking on the sensor, so I assume the remote is working.
To verify if you have a defective/failed device you are either going to have to plug the Express into a different TV or plug another HDMI device into your TV (laptop/gaming system/dvd players etc) to verify your TVs HDMI ports are working. Also, it is suggested that you use the power adapter (plugged into wall), and not power the Express from the TV's power USB port if you are currently doing so to ensure device is getting proper power.
If issue still persists after trying the above, could likely be your Roku Express has failed or is otherwise defective. If less than a year, thae should qualify for replacement under warranty. https://support.roku.com/article/208757058
I only have 1 TV and I know that at least 2 of the HDMI ports work because I have Nintendos plugged into them and have never had an issue getting signal to the TV from my Nintendos. I am using the power adapter, I plugged the Roku into a power outlet. My son is going to help me tomorrow, if we still can't get it to work, thank you for the link I will try figure out how to get a replacement for it, I bought it on Amazon.
Since the other HDMI devices work in the port, safe to assume there is a problem with the Express unit and not your TV. I re-read your posting and saw that you pressed reset button on Express.
Try pressing and holding that reset button for 30+ seconds to factory reset the Express device while unit is powered. Since you won't be able to see what's going on, longer the better. If that doesn't resolve issue, then you can be confident you have a failed device. Good Luck and post back with any updates.