Those using TurboTax with Vanguard may face two sets of forms: one for mutual funds, one for brokerage accounts. Vanguard upgraded accounts and may have left a mixture of tax forms in the wake of the change.
I discovered missing transactions, and upon reaching out to Vanguard discovered I needed to run TurboTax imports twice:
1. import "Vanguard - Brokerage Accounts"
2. import "Vanguard - Mutual Fund Accounts"
Only when I finished the second "Vanguard" import did I see the correct tax information. You can see if this applies to you by visiting "Tax Center" in your Vanguard account. If you see a "1099 consolidated" and a "1099-B" separately, try importing with both account types.