Click on Upgrade on the left side of the program screen if you have not yet filed the 2018 tax return using the online editions.
Your message shows you are currently using the TurboTax online Deluxe edition. If your question concerns accessing prior year online tax returns, then just pay for the edition you are currently using.
To pay the TurboTax online account fees by credit card so you can access your prior year online tax returns, click on Tax Tools on the left side of the online program screen. Then click on Print Center. Then click on Print, save or preview this year's return. On the next page, to pay by credit card, click Pay Now. On the next screen just click on the Continue button. The next screen will show a review of your Fees, click on Continue. Complete the next screen to pay by credit card and click Continue.