I can't change careers when a opportunity comes up

Right now my sim is in the military career. When a opportunity came up to change to the police career, I pushed "change career".  The opportunity popped up 3 different times when I was going to get a promotion. The first time I said "keep job", the second time I said "change job" and it didn't change. He still went to work at the military base. The third time I pushed "change career" and it still didn't change. Am I doing something wrong? I want him to change to the police career but I don't want him to start at Police⚽. Please help me!