You may have forms in your return that are not available yet, have overrides, or you may have forms on your return that cannot be e-filed.

When a tax return can't be e-filed no matter what you do:

https://ttlc.intuit.com/community/e-file/help/when-a-tax-return-can-t-be-e-filed-no-matter-what-you-...

IRS forms availability table for TurboTax individual (personal) tax products

https://ttlc.intuit.com/community/forms/help/irs-forms-availability-table-for-turbotax-individual-pe...

State forms availability table for TurboTax individual (personal) tax products

https://ttlc.intuit.com/community/forms/help/state-forms-availability-table-for-turbotax-individual-...