How do I get a job advancement?

[Senteria]

I read you need to be at least level 20. My Mentalist is lvl 24, but I don't think I advanced her. Is this done automatic or do I have to do something?

[Thaecrasis]

It should be automatic; every troop I've had that reached lv 20 has been promoted. I'd say some sort of bug happened when your mentalist leveled from 19 to 20. I bet Craig can give you some code to implement into your next map file to initiate the promotion for them though, probably.

[CraigStern]

Is this done automatic or do I have to do something?

It's automatic. Do you remember how / when  she hit level 20?