Lexor: But you are trying to buy new units or add units from garrison to your army? I do not have any confirm button when I am trying to add only when I am buying.
EDIT: I am talking about situation like in attachment - what happens if you click on 9 Inquisitors in garrison?
Transfering from garrison.
Detailed description of my actions:
Loaded game I had abandoned for some reason long time ago. Hero is standing right in front of castle. In garrison of castle there is 24 peasants, 25, gryfs and 22 archmages. In my army there is bunch of Dwarves and 47 Horsemen. I switch horsemen with peasants and disband peasants, then I hired another 47 Horsemen and when I click on horsemen stationed in garrison I get new window where I can transfer any amount of horsemen to my army only the confirm button is greyed out because of "Not enough Leadership to hire troops" message.
Also my reserves were full. I tried with reserves empty too but it makes no difference.
I would prove it with screenshot but for some reason when I press Printscreen in-game it only captures my desktop.