Have you tried the STB on another TV?
How did you connect to TV? If using coax, did you set tv tot he correct channel (try both 3 and 4).
I added another settop box yesterday using an older Apex tv. I have tried everything and only have a blank blue screen. Help!
If it's the *digital adapter* unit, rather than a set top box - try a re-scan of the channels.
Try in home agent if you're not sure.