I’m having this same issue with both my roku devices (“roku Express” and “roku player”) and my LG tv. I’ve switched ports, HDMI cables, powered on and off, changed input source. Can’t get either to work. And they both light up when plugged in. I know my tv is recognizing them because when I plug one into an HDMI port, that input source pops up on my tv. Only thing I haven’t tried is updating the software. When I went to settings in the iOS app I see “system info” not “system” and there’s nothing under system info about an update for either device. I updated my app and now I don’t even see a “settings” but there is a menu with the same “system info” on it. Are the instructions you’re providing for updating the software for on the actual device? I can’t access the settings menu on the device because my tv only says no signal.
I just bought a ROKU ultra today and I am having the same problem. Like another replied, my tv is an ELEMENT. I have my ROKU set up on HDMI3. Switched it to HDMI2 to play on my nintendo switch a bit and then turned off the tv. Came back, turned on tv, switched to HDMI3....and nothing. Roku only comes back on when I unplug, then plug back in.