In fact, he's been unable to patch up his relationship with his tower (don't ask) for some time, because they had a fight once and "Valentines never apologize." However, when it becomes a matter of life and death, he is able to overcome his pride and say sorry.
Exposition of the series says, "The more he feels, the less he articulates." It's eventually clarified that he is literally physically incapable of expressing emotions in words, at least most of the time.
Being a Pop-Cultured Badass, she figures it out very quickly - and is just as tongue-tied herself.