I started my 2019 taxes a month or so ago using Turbotax. I logged in the other day to finish and it was gone. How can I access the information already entered?

Online closed back on October 15.  2019 is now the prior year.  Online and Efiling is now closed.  You have to print it out and mail it now.  Or switch to the Desktop program to finish.

How to finish a prior year online return   

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-started-in-turbotax-online/00/26322

If you paid for the Online version you can ask support to give you the Desktop download.  Contact Customer Service 5am-5pm Pacific M-F

https://support.turbotax.intuit.com/contact/

See this TurboTax support FAQ for completing a 2019 tax return originally started with the online editions - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-started-in-turbotax-online/00/26322

If you paid for one of the 2019 online editions contact TurboTax support and they can push a 2019 installation file to your download account at no charge - https://support.turbotax.intuit.com/contact/

You have to sign onto your 2019 online account using the exact same User ID you used to create the online account.

Close all TurboTax windows on your web browser (including this one).  Copy and paste the account recovery website link onto a new web browser window and run the tool.

Use this TurboTax account recovery website to get a list of all the User ID's for an email address.  Run the tool against any email addresses you may have used - https://myturbotax.intuit.com/account-recovery

If none of the user ID's received will access your 2019 account, then use the option shown in blue on the account recovery website, "Try something else"

If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created.  TurboTax does not store online any returns completed using the desktop editions.

To access your current or prior year tax returns sign onto the TurboTax website with the User ID you used to create the account - https://myturbotax.intuit.com/

Scroll down to the bottom of the screen and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Download/print return (PDF) or Download .tax file