Look for an ACTION NEEDED! email from turbotax@intuit.com. It will give you a brief explanation of your rejection and how to fix it.
If you did not receive an email then sign in to TurboTax, select Fix my return, and you will see your reject code and explanation.
How do I fix a rejected return?
Please see this Turbo Tax help article for more information.
What is IRS Form 8615?