Return key on macbook pro doesnt work anymore

Hi, After my son had been messing about with my macbook pro, the return / enter key doesnt want to work anymore, I have removed it and checked under it for dirt / debris but cannot see anything.

It presses as normal but wont do anything and just beeps at me , its very frustrating, typing this on imac as can only get one long sentence on macbook !

Any help most appreciated.

Thanks

My guess would be liquid damage. You may want to quiz him further about exactly what's been done.