If you didn't receive your second stimulus check, you should have been able to claim the Recovery Rebate credit on your 2020 tax return. The stimulus is just an advance on that credit. You stated that you did this.
You should first check your IRS account to see if you can figure out what has happened. It could have been issued and never received, or it could have been stuck for some other reason. The account should be able to provide history and information. The next step would be to communicate with the IRS through the account. Here is the link to see your Online Tax Account.
The following are two other links that can help with regards to stimulus payments:
If you are still waiting for your stimulus payment, you can check the following TurboTax link for help.
For refund inquiries, please visit the IRS website to see their refund status tool.
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