Turbo Tax started out giving you the 4200 as soon as you entered your dependent. If you didn't see a big refund in the monitor it was probably just deceasing a tax due you had and showed you a smaller refund.
If you don't think you got the 2800 deposit from the IRS then Request a trace for a missing third Stimulus payment
https://www.irs.gov/newsroom/questions-and-answers-about-the-third-economic-impact-payment-topic-j-p...
