You could not have been using Turbo Tax 2019 for more than 1 year. It didn't come out until November 2019.
Turbo Tax asks for the License Code each time you start
I exaggerated a bit. Yes, I've been using it only since last November. I managed to contact Intuit tech support and it turns out that Windows update sometimes causes this problem. Anyway, I got the license number and am all set.