No, you don't need to start a new return. If your return was rejected, it means it has not been filed yet. You can open your return to fix the issue and re-file it once it is corrected.
To confirm the 3rd stimulus check,
- Open your return
- In the search box, type recovery rebate credit and select the Jump to link at the top of the search results
- Follow the instructions to confirm the amount received
- If you don't see the screen below, it could mean your income is over the limit.

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