TurboTax is aware of the problem and they are working on it. There might be a fix next week. Check for a software update next Thursday.
In the meantime, here's how you can work around the problem. Go to forms mode, click Open Form, and open Form 1095-A. Enter the policy number in the "Create new copy" box. Then go back to Step-by-Step mode and try again to enter the form. It will tell you that your 1095-A needs review. Click the Review button and proceed through the interview to enter your 1095-A.