The license code is only used on the 2019 TurboTax desktop CD/Download software that you purchased. After you install the TurboTax software on your personal computer you will be asked for the license code.
The TurboTax online editions do not require a license code and there is no reason to use the online editions since you purchased the TurboTax software to be installed on your computer. The TurboTax desktop and online editions are totally separate program with different price points.
See this TurboTax support FAQ for a license code - https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/01/852973
You seem to be posting from online TurboTax. If you purchased the CD/download software you open up the program from your own hard drive---just like you do for the other programs you have installed to your computer. You do not log in using an account or username.
I start the downloaded Deluxe version but it doesn't return me to the return I'd nearly completed - it wants me to start over with a new return. Can I find the earlier one? Thanks!
In the download, you can prepare 5 returns. Are you clicking on the correct return? You will be able to see the returns started and completed when the program launches.