I got a Letter 12C from the IRS. Where can I see all the supporting documents that TurboTax already submitted to the IRS, so I can figure out which ones might be missing?

This Letter 12C did NOT request Form 8962, so the help article here does not apply to me. Neither I nor my husband have health plans through Healthcare.gov. https://ttlc.intuit.com/community/health-care/help/the-irs-is-requesting-form-8962/00/27409

The info requested in this letter includes:
- A copy of pages 1 and 2 of your return.
- Amounts and dates of all estimated tax payments you made for this tax year (if applicable).
- Any supporting documents verifying income and withholding.

I'm at a loss, because all of these docs should have been submitted by TurboTax in my original return. Why would they request them again?