can't enter code and start taxes

If you are referring to a tax year 2018 return, the TurboTax online editions have permanently closed.  To complete a 2018 tax return that was started with the online editions see this TurboTax support FAQ for instructions - 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 are referring to a 2019 tax return, the TurboTax online editions should be available in early December.

If you purchased the TurboTax software to install on your computer for tax year 2019, either CD or Download, see this TurboTax support FAQ for the license code instructions - https://ttlc.intuit.com/community/tax-topics/help/i-can-t-find-my-license-code/00/852973

can't find code

can't find license code

Return to the install screen and enter the code to continue.You can copy/paste the code into the entry fields.

You can also find additional information and download help in the links below:

Activating TurboTax CD/Download software

My code doesn't work

I can’t find my license code