For 2021 the rules for the Child Tax Credit are very complicated. The fact that you live outside the U.S. adds complications, and you have not given anywhere near enough details to know if you qualify for the Child Tax Credit.
Are you asking about the monthly advance Child Tax Credit payments, or about the Child Tax Credit on your tax return? The monthly advance payments have ended, and as of now they will not be continued in 2022. Since you live outside the U.S., you would not have been eligible for advance payments anyway.
If TurboTax is saying that you are not eligible for the Child Tax Credit on your tax return, it's probably right, unless you made a mistake entering something or answered a question incorrectly. Here are some other considerations, but this is not at all a complete discussion of the rules.
If you are a U.S. citizen or resident alien living in a foreign country, you are probably claiming the Foreign Earned Income exclusion, and possibly the housing exclusion or housing deduction. Those exclusions are added to your Adjusted Gross Income (AGI) to determine your Modified AGI (MAGI) for the Child Tax Credit. With one child you cannot get any Child Tax Credit if your MAGI is more than $239,000 ($439,000 if you are married filing jointly).
If you lived outside the U.S. for more than half of 2021, you are not eligible for the refundable Child Tax Credit. You could still get the nonrefundable Child Tax Credit, but the nonrefundable credit cannot reduce your tax to less than zero. If your tax is already zero before the nonrefundable credit, or the nonrefundable Child Tax Credit plus other nonrefundable credits reduce your tax to zero, you will not get any payment for the Child Tax Credit. You might still be eligible for the refundable Additional Child Tax Credit.
