According to this IRS FAQ question h10, you may request the IRS trace the payment. If it is determined the payment was not received or was returned to the IRS, IRS records will be updated, and you can exclude the payment from the aggregate amount of advance Child Tax Credit payments you report on your tax return. This will allow you to claim, if eligible, the missing payment with your Child Tax Credit on your 2021 return. Contact the IRS, as soon as possible, from 7 a.m. to 7 p.m. local time at 800-908-4184. When you call the IRS, you must provide the following information about the missing payment: the payment date, method, status, and amount that is displayed in your Child Tax Credit Update Portal.
You may need to file an extension to allow time to complete the process. Here is a link with instructions for filing an extension using TurboTax.
Since today is the day to file the extension, should I calculated the estimated tax assuming the credits were paid so I do not UNDER ESTIMATE the tax liability and face penalties ??