Doing taxes from 2016, adding an additional state. To purchase in the software, can't confirm address. Can I purchase an additional state for 2016 somewhere else?

Yes, you can purchase TurboTax products for 2016 at this link:  https://turbotax.intuit.com/personal-taxes/past-years-products/2016/

This only allows me to purchase everything over again. I already bought the Deluxe version, I am only trying to purchase an additional state for 2016 and it won’t let me.