No video or sound on TV when using RGB SCART cable
Check that the SCART socket you have plugged the SCART cable into is an RGB enabled port (this is usually AV1 or EXT1) and that you're not using a SCART switching box, which may not support RGB, only composite video. Also check that your television is switching into RGB mode correctly. Some TV sets display an 'RGB' message in the top right of the screen for a short duration when selected. This should be automatic when you turn on your console/ computer, however, if this does not occur you maybe able to manually select the RGB channel pressing the Mode/AV select button on your remote control until you hit the RGB channel. Also check that none of the pins are bent on the Audio/video plug and that all the SCART plug pins are straight.
If you are using a ROM cartridge game used commonly with video games consoles, try using a variety of games to see whether the first game cartridge was faulty. Cleaning the copper contacts on the edge connector of a ROM cartridge game will often fix the cartridge. Metal oxidisation of the copper contacts over time render the cartridges useless, however, in most cases cleaning the copper contacts with either an electronics cleaning solution or light cleaning with a high grade sand paper can clean the contacts. Do not clean the copper contacts with water and do not submerge the ROM cartridge in water.
Please refer to the cartridge cleaning tutorial at RetroRGB.com