The IRS made the Child Tax Credit fully refundable in 2021 and provided Advance Child Tax Credit Payments to people who claimed a qualified dependent in 2020. Since some taxpayers do not claim a dependent every year, a taxpayer could have received the Advance Child Tax Credit payments in error because they are not claiming the dependent on their 2021 tax return.
You simply need to enter 0 for the payments, since you didn't receive any and continue on. To get to the Child Tax Credit entry screen you can use the magnifying glass icon to search Child Tax Credit.