Roku 4k express is stuck on bouncing Roku screen. Reset button simply kills the picture. I have changed cords, and tried factory resetting by holding the reset button for 45 seconds multiple times and it does nothing.
Verify that you are plugged into the wall outlet and not back of your TV. Unplug power for a couple of min and then reboot and see if it will attempt to connect to a mobile hotspot (if available to you).
When pushing the factory reset button for 45sec, make sure device is powered during this procedure. (again power from the wall, not TV).
If device fails to factory reset, I would suspect a bad/failed device. Likely still under warranty as these devices were recently released.