It is a knight wielding 2H weapons. I have tried few tests as well. I started swapping her weapons and unequiping all or swapping her armor sets as well to see if any changes. Still not working. I fear that it could be a bug that is triggered at every beginning of the game. I hope not.
@Mon , how far are you in the game? Can you test something for me? Have your Warrior learn Magical Training and than use something that would use mana (scroll, etc,). You might have to reset traits / skills to be able to do it. I want to know if your main character using mana is the hiccup here. Since Warriors can't use mana, they can't knock things loose so maybe if they use a magical item that uses hitpoints instead of mana, it will do the same?
Use a back-up save slot so you can load your warrior before messing with it.
I'm level 20 knight that equips 2h weapons. I tried resetting my traits and skills and kept all to 0 and tried resetting Hirge as well. Only have her learned retribution, still no progress. I tend to get her to my team as early as level 5. I wonder if that has something to do with it. I'm currently playing rogue after completing shards of fate on my warrior. I'll see if there's any difference this time.
My working theory is that Hirge's Retribution skill won't work until the Main Character has a change in mana points. I'm not sure why that would be the case, but that seems to be an observable pattern.