Because you don't owe income tax, you can't get the Child Tax Credit. It can only be used to reduce your tax, it can't add to your refund if you don't owe tax.
There is what's called the "Additional Child Tax Credit" which is a partial version of the Child Tax Credit that can be refunded even if you don't owe tax, but this is based on how much you earned from working. Because your earned income is low, you are not getting the full amount.
The Child Tax Credit was made fully refundable on 2021 tax returns as a special stimulus measure, but it is back to the normal rules now.
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