Trying to get cyborg race but when I insert the fist nothing happens?

So I got a fist of darkness for cyborg race i step on the spot where you'd stand if you were to start a law raid and i click the button with the fist of darkness in my inventory but all it says in green text is "Please supply a<Core Brain> to continue." and the door is shut. Now this might not be related but before some of the sea 2 islands were redesigned i had quit the game for over a year and I have faint memories of trying to get cyborg and defeating law. Can anybody help?

https://preview.redd.it/j8n6hdbs1etg1.png?width=1064&format=png&auto=webp&s=a9102eeb426668542cf08cd40e12a6e62b8a2c30