Things You'll Need
Instructions
Turn off your GBA SP, remove the Gameshark cartridge, and disconnect your game. Try the game in your GBA SP to make sure this is not at fault. Reconnect all components and try again. Nonworking cheat cartridges are often simply the result of a loose connection.
Disconnect game cartridge, Gameshark, and game console. Wet a Q-tip with a small amount of rubbing alcohol and clean the contacts inside the Gameshark and GBA cartridge. Reconnect all components and try again.
Inspect the contact pins in the top side of the Gameshark, where GBA games are inserted. Incautious game insertion can lead to these pins' being bent out of shape, resulting in failed game connection. If necessary, carefully bend the pins back into shape using a pair of needle-nose pliers.
Reset your Gameshark and try using fewer cheats. If your device is booting correctly but refusing to run your selected cheats, you may have chosen incompatible codes. There is no way to know whether codes are compatible except to try them out together. Try your codes one by one until you can isolate the code that is causing you problems, then re-input codes into your device without using this code.