If your Sky tvLINK is not working, first check that it is receiving power through its RF connector. The RF outlet power supply is a trip switch, so the process of isolating the power to the tvLINK then restoring it usually resolves this type of problem.
Please make sure that your Sky box is switched off at the mains or unplugged before carrying out the following procedure. Please note that connecting the RF lead without a tvLINK, to either a TV set or video recorder directly, when the power supply is turned on, can damage the equipment.