1099-B cost basis is missing. I checked the "cost basis is incorrect ormissing" box but Turbo Tax won't let me continue. It keeps going back in circles.

You may want to log out, clear your cookies and cache, and then log back in to see if that helps. 

 

Here's how:

 

Each browser has a slightly different method for deleting cookies. Choose the browser you're using:

• Internet Explorer
• Mozilla Firefox
• Google Chrome
• Safari
• Safari for iOS (mobile devices)

 

A full or corrupted cache can cause problems in TurboTax, so sometimes you need to clear your cache (that is, remove these temporary files).

 

Here are the official instructions for the most popular browsers:

• Google Chrome
• Mozilla Firefox
• Microsoft Internet Explorer 11 (use the drop-down on the upper right corner of that page for earlier versions)
• Microsoft Edge

Apple's official support site doesn't appear to contain instructions for clearing the cache in Safari. Your best bet is to search the Internet for clear Safari cache or similar search terms.