Can you give me any tips on how to draw out alters who may be hiding? We have one who I'm having difficulties accepting is here, even though he's fronted a few times, and I feel like my reluctance to acknowledge him as being here has - understandably - made him nervous. For the other, we're not actually too sure if she exists save for a temporary title/name we associate with her and a general idea of what she feels like/what her personality might be like.
You could try talking to her/finding them in the headspace. Without knowing too much about their personalities/interests it’ll be a bit hard to draw them out, but headspace meetings and journaling can work really well. You might even have luck with meditation.
Be patient! Most issues like this resolve themselves.