“She is hidden from the eyes of all living.” It seems at this point in Job’s narrative (or perhaps a few verses earlier or later), wisdom becomes personified and presented as if she was a person by itself, and God is acquainted with her. This is very poetic and not out of character with the Book of Job itself, which is Hebrew poetry. Wisdom is presented as a woman here in Job and in Proverbs, and the Hebrew word for “wisdom” is feminine (see commentary on Prov. 1:20).
“the birds of the air.” The Hebrew is literally, “the birds of the heavens,” but the Hebrew word “heavens” is always plural, there is no singular word “heaven” in Hebrew. In Job 28:7, the falcons of the air cannot see the riches buried beneath the earth, and here they cannot see wisdom, which is hidden in God.