if you're due a refund, there is no reason to file the return because it is forfeit. if the IRS has requested the return or you owe see this link for where to file based on your resident state. realize that the 2017 app you used may produce the wrong results because no updates are available and it's really based on 2016 tax laws.
https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
