Have you hooked the Hopper up to another TV?
The problem is one of three things... the TV, cable, or Hopper. Here's how you eliminate each:
1) Hook another device (DVD player, gaming console, Roku, whatever) to the TV using the same input and the same cable. Do you have a picture? If yes, the problem is with the Hopper. Power cycle and check settings. If no, go to step 2.
2) Use another HDMI cable between the TV (same input) and Hopper. Do you have a picture? If yes, the problem is with the cable. Continue using the new one. If no, go to step 3.
3) Hook the Hopper up to another TV using the original cable. Do you have a picture? If yes, the problem is with the TV. Power cycle the TV and try another input. If no, go to step 4.
4) You have multiple problems.
The more detail you can post on what EXACTLY you've done, the easier it will be for us to try to help you.