Make sure with the help of Elisa Viihde channels instructions that you are trying to watch the channel from the correct channel slot. The same instuctions also help you further with problems related to channel visibility.
Also make sure that your TV is using the correct input source for the set-top box. The source can usually be changed using the Source, Input or “arrow in screen” buttons on the TV remote.
More detailed instructions for selecting the input source can be found in the user manual of your own TV.