@Sam613613 - in 2021, the child tax credit (the $3600 / $3000) is as xmasbaby0 explains. So since you and the children did not live in the US for at least 6 months , you are not eligble for that.
but the 'old rules' (pre-2021) were still in effect for those not eligible for the 2021 version noted above (and those pre-2021 rules are back in effect for 2022). But they are non-refundable credits, meaning if you did not have a tax liability, there is no child credit (the $2,000) under these rules either
