What do you mean by "sign in?" If you have desktop software that requires a license code, you download/install it to your own hard drive and work on it by updating the software and opening the program from your own hard drive. You do not "sign in" to use desktop software.
Where did you get the License Code? Did you get the program installed or are you trying to download the program?
How to download Turbo Tax if you can't use the CD
How to install on Windows
How to install on Mac
How to activate the Desktop CD/Download program
@Bayside2426 What did you pay for?
Did you purchase desktop software (CD/download)? You do not "log in" to use desktop software. You download it, enter your license code, update it, and open the program from your own hard drive.
Access your downloads here
To find your license code:
And it is too early to try and use online TurboTax. Online for 2020 is not yet open.