What year was the amended return for? It could not have been 2016 taxes since Turbotax could not prepare a 1040X until after February 15, 2017.
They can't tell you to go back online and refile an amended return because amended returns can't be filed online unless you use a real accountant.
What is a form 740X? Is that a federal form (used for certain business taxes only) Or is that a state form? If so, what state? Did you call the state and IRS separately? Did both the state and the IRS lose your forms? Or maybe you mailed the state and IRS forms both to the IRS?
Much is still unclear here.
