The IRS has not Finalized the Form 8915-B so until that happens there is nothing TurboTax can do but wait for the IRS. When the IRS finalizes and approves the form then TurboTax will be able to supply the form for filing.
IRS website for the draft 8915-B - https://apps.irs.gov/app/picklist/list/draftTaxForms.html?value=8915-B&criteria=formNumber&submitSea...
