You need to programme it with the correct code for your TV: https://www.sky.com/help/sky-tv/sky-tv-plus/sky-plus-equipment/my-sky-remote/program-your-remote/art...
Edited to add: with apologies @Rene4, it appears that Sky have removed their Sky+ remote code finder. You could try searching online, or post the make and model of your TV here, someone may know a code that works. If all else fails you could scan through all the codes stored in your remote to find one that works. To do that:
Press TV
Press Red and Select together until the red LED flashes twice
Press the TV and power buttons repeatedly until your TV switches off.
Then press Select to store the code.
