Are you sure you are not confusing the Recovery Rebate and the Child Tax Credit? There are multiple types of credits, refundable and not, and these two depend on qualification. For instance, you have nonqualifying parents with 2 qualifying children for the EIP/RRC stimulus payment they did not get in advance?

https://www.irs.gov/coronavirus/economic-impact-payment-information-center

https://www.taxpayeradvocate.irs.gov/covid-19-home/3rd-eip-and-2021-rrc/

More details regarding this taxpayer might be helpful.