Battlefield Valkyria 2 Why can't some people change their potential?

Because those people haven't realized their potential, you can look at other jobs. If the asterisk and p are displayed in the upper left corner of the task unit, it means that this person's potential has been learned under this unit.

As shown below?

I know what you mean, so I will ask you to change your job. The third and fourth potentials are related to the arms and can only be learned under the arms. Only when the asterisk and p are displayed in the upper left corner of the arm can this potential be learned. If you don't understand, just give it to Q.