@s Command Blocks doesn´t work

I tried to create a command with @s to teleport the player that triggered the redstone signal, but nothing happens! The command block says the "entity @s cannot be found". I triggered the redstone signal with a pressure plate. Even if I put the pressure plate on the command block, the same error message occurs. It´s unimportant how I trigger the command block (Buttons, Lever, Pressure Plates), it never works!