Was the 2016 return prepared in Online TurboTax?   If you used a CD/download product, the 2016 return will not be in an online account.   

If you used Online TurboTax, but find no evidence of the prior online return, then you likely have multiple accounts and signed into the wrong one.  To get a list of your User IDs and recover account access, you can use the tool at the link below.  Try using your phone number first.   After that, if necessary, then run the tool on your email address(es) you can access.

NOTE: Before running the account recovery tool below, log out of all Intuit accounts including this user forum, or you might end up in a loop.  Then clear your browser Internet cache, close your browser, then reopen it, and go to the link below.  You may wish to copy this link so you can paste it into the new browser session.

https://myturbotax.intuit.com/account-recovery

If still no luck after running that on your phone number and email address(es) that you can access,  here's another method:

Go back to the tool again, but this time leave the data field blank, and choose the small blue link that says "Try something else", and it will look you up by SSN and other parameters.