If the device works on another TV and doesn't work on another, it would appear to be a connection issue. Have you tried replacing the HDMI cable being used to connect the device? Have you tried using another HDMI port on the TV as well to see if that resolves the issue? How is the device being powered? Is it being plugged into the TV USB port or is it plugged into a wall outlet with the provided cables?
Stick worked for about a month and quit after doing the the software upgrade on my stick. Have tried all suggestions on this site as well as the internet to correct this black/dark screen except replacing router or using a second hdmi port (there is only one on my SONY TV). Have tried the stick on two other TVs where I normally use ROKU Ultras and it does the same thing. This problem seems to be persistent, pretty straightforward (software upgrade related), relatively easy to correct (by going back to the previous software version, replacing the defective product or refunding the money paid for the malfunctioning product) and accompanied by a consistently unresponsive ROKU, Inc.
Looking for a solution. Best Buy will not take the stick back and they told me to contact ROKU. Have tried to find a way to contact ROKU to no avail.
@Dbrymer87 Thanks for the note. You'll want to make sure you are powering your device using the included wall power adapter. You can also try using a different micro-USB cable and/or wall power supply, such as one from a mobile device, to see if this allows your device to start normally. We'd also recommend trying to replace the HDMI cable that connects your device to your TV, or plugging the HDMI cable into a different port on your TV.