Why isn't this working, please help? (PORTAL DLC)

Hi all, what did I do wrong, why is the pressure plate not going down? Are the rat food and foot not heavy enough? I even got the cake on there. /s

https://preview.redd.it/nzdm2spea2nb1.jpg?width=1920&format=pjpg&auto=webp&s=41e59b2ac16213baf258de9b56fe031b01ef33ea