This is happening to a number of people. The IRS has not provided guidance. It may be that they are verifying dependency.
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Ok, and even though I’ve already received my tax refund in the beginning of the month, that should have been proof of the dependency correct? Will I eventually get it, even though I’ve already received the $1,200?
You will receive a letter within 15 days that may give you some guidance on what to do. If all else fails, you can get it on your 2020 tax return when you file it. The payment is actually an advance on your 2020 taxes and any discrepancies will get resolved when you file your 2020 return. I know that's not a good solution for someone who needs the money now. Wait for more info from the IRS about what to do.
Was the child no older than 16 at the end of 2019? Did you get the child tax credit on yiur 2019 tax return?