TurboTax online accounts cannot be combined or merged. 

If you completed the 2018 tax return using the new online account then just download the PDF of your return.

To access your current or prior year online tax returns sign onto the TurboTax website with the userID 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)

However, if you completed the 2018 tax return with the account that was deactivated, then contact TurboTax support for how to re-activate that account.  Once activated download the PDF of the 2018 tax return.

Use this website to contact TurboTax support during business hours - https://support.turbotax.intuit.com/contact/
Support can also be reached by messaging them on these pages https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax