I need help with m effect game for X-BOX?

i am at the citadel were saren is about to let in the Sovereign take over. the character i am using is a customized female shepard (solider cl) im trying to make saren kill himself. i watched a youtube vedio on how to do. but for some reason it wont allow me to. all of her charm and intimidation are full.did i do something wrong? has anyone else had this problem? how do i fix it