The first thing you need to do when you encounter this issue is make sure you have secure connections between the device that is outputting the video and the device that is displaying it. For example, if you computer is hooked up to your TV, make sure the video cable is firmly plugged in and connected to the computer AND the TV.
If you are still experiencing issues it could be due to your television being on the wrong input setting. If you follow the video cable from your output device to the TV, you can see the way the TV port is labeled. For instance, many televisions will have their HDMI ports assigned a visible number 1-5 that you can see just by looking on the outside of the TV where you plugged in your connected video cable. Once you have identified the name of your connection, use your TV remote and press the "input" button. You should be able to choose and access the connection that you identified earlier.
If you are still having issues then it could potentially be a hardware issue (like a bad cable or bad port). If this is the case, and you have tried the steps above and still are receiving a "no input" error, please alert the IT office immediately so that we can remedy the problem ASAP!