How was it prepared? Was your 2017 return prepared with Online TurboTax? If so, log in to your account and look in the section "Your Tax Returns & Documents." Expand that section and choose tax year 2017, and look for a link to "download/print the PDF." Do you find evidence of your return there OK, but when you try to download, does it ask you to pay? If it was prepared in Free Edition last year, access will be locked. If that's your situation, we can tell you how to pay to unlock your 2017 return. The method to unlock it depends on what all you have done with your 2018 return.
If you find no evidence at all of your 2017 online return in that account, we can tell you how to look for multiple accounts. A return prepared in desktop software (CD/download) will not be in an online account.