Most users experiencing this issue have more than one TurboTax account and don't realize it. In order to access a return, you need to use the EXACT login (same username and password) that you used when preparing the return. I'm linking you to a TurboTax FAQ below that will explain how to find out if you have multiple accounts. It also offers other options that may be the reason you can't find your return.
https://ttlc.intuit.com/community/accessing/help/why-can-t-i-find-my-return-in-tax-home-or-my-docs/0...
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*** 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.***