There are many reasons some players don't get ranked properly by recruiting services. Could be they had a superstar playing in front of them, didn't attend any camps, plays at a school that is not known for football, or has a very common last name like Smith and just gets overlooked. That's why schools don't take that much stock into star ratings.
Case in point, is Michigan's latest commitment on Monday afternoon from NC, athlete Jaden Smith who is 6'3 and 201 pounds. He is not ranked by 24/7 but has offers from the SEC, Big Ten, PAC 12, and ACC.