Between the 2 screws with white wires, there is a little tab that connects the 2 screws. Between the 2 screws with the black wires, that tab is missing, That would explain why you have no power to one side of the outlet. So now the question is was that cut out for a reason or was that something that just happened. Can you tell if it has been cut or melted or? I would not fix it until you have more info!