The screen page does not have a Start or Revisit button for Step 3 as shown in this screenshot?
If there is no start button, then close the TurboTax program. Clear cache and cookies on your web browser. Close the web browser. Re-open the browser and sign back onto your TurboTax account - https://myturbotax.intuit.com/
Click on File on the left side of the screen to return to the page for filing your return. If the problem persists then change your web browser. Google Chrome seems to work quite well with the TurboTax online editions.