Most often, users experience this issue when they have more than one TurboTax account and don't realize it. In order to access an online return, you must use the EXACT account (same username and password) that you did when you prepared the return. I'm giving you more info below with assistance in finding out if you have multiple accounts, along with other possibilities. Hope this helps!
https://ttlc.intuit.com/replies/3290682
*** I am NOT a tax expert. I am a seasoned TurboTax user, and volunteer to provide assistance to TT users. Nothing I post is to be considered TAX ADVICE; I bear no legal liability for responses.***
