It should be available to import, since Vanguard is a TurboTax Partner for both the Brokerage Account and the Mutual Fund Account. Try turning off the two layer long enough to import it, and then re-instating it.
You may have to enter the transactions manually by clicking on the I'll type it in myself option instead of importing it.
Here are some more resources for importing the transactions:
How do I enter a large number of stock transactions in TurboTax Online?
Where do I enter a 1099-B?
Where do I enter a 1099-INT?
Where do I enter a 1099-DIV?
