I have a 17-year-old dependent in 2021. Turbo Tax says 17-year-olds qualify for a $3000 credit, but is saying that my 17-year-old is disqualified. Why?

I have read the standard information about the Child Tax Credits.  My income is within the qualifying range, and my dependent child was 17 years old as of 12/31/21, so should qualify for the $3000 credit.  However, when I enter my information in TurboTax, I'm receiving the message "It turns out you don't qualify for these credits."  However, I'm not receiving any explanation as to why... it just says that my dependent "had another disqualifying situation."  Can someone please explain why I'm receiving these messages that I don't qualify?