In order to amend your state tax return in TurboTax, you have to "amend" the federal return first. If the federal return doesn't need amending, then don't file it - just file the state amended return.
TurboTax creates a state return using the information in the federal return; that is why you always prepare the federal return first, because the information automatically flows to the state program. Also, most amendments to a state return are the result of changing (amending) the federal return - another reason you have to amend the federal return first, before you are able to amend the state return.
Even if your federal return doesn't change, you still have to go through the federal amend process first. That will allow you to access and change (amend) the state return. It allows you to update the state return based on changes to your state interview answers and changes in the state's tax laws since originally filing.
