My timeline does not appear.  Now what ?

To access your prior year returns, you will need to sign in with the same TurboTax account that you used previously. Please note, there can be multiple TurboTax accounts associated with a single email address.

If you are in the wrong TurboTax account, please follow the instructions below after logging out.

https://ttlc.intuit.com/replies/3302318

Here are the steps to find your prior year's return once you are in the correct account
https://ttlc.intuit.com/replies/3301525

You can also request your transcripts from the IRS through this link.
https://www.irs.gov/individuals/get-transcript

TurboTax says that I did not file in 2015 but I know that I did.

Many people have multiple TT accounts and forget how to access them.  Log out of the account you are in now.
Account recovery
<a rel="nofollow" target="_blank" href="https://myturbotax.intuit.com/account-recovery/">https://myturbotax.intuit.com/account-recovery/</a>
Or did you use the desktop version of TurboTax?  If so, the files are on your own hard drive.
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/1901535-forgot-your-turbotax-user-id-or-password">https://ttlc.int...>