You may need to clear your browser's cache and delete the cookies stored on your computer. A full or corrupted cache can keep TurboTax from functioning properly.
Please see the below FAQ for instructions on how to clear the cache and delete cookies.
Clear Cache: here
Delete cookies: here
Also, try refreshing your browser and even try using a different browser if the issue persists. If none of these resolve the issue, please contact Customer Support for further assistance.