did you enter summary transactions that appear on lines other than 1a and or 8a of schedule D?
then the IRS wants to see the details of each trade. PDFs cannot be attached to an e-filed return. Thus, what's required is to complete form 8453 (Turbotax should have done this for you) and mail it with the 1099-B following Turbotax mailing instructions for this form. use a tracking service.
if this is not your situation, then contact support
5am-5pm Pacific Time (8-8 Eastern) Monday - Friday
https://support.turbotax.intuit.com/contact
800-446-8848
