I think you're misreading something on the TurboTax box. Any TurboTax software is for only one specific year. It can never be used "back through" prior years. If you bought TurboTax for 2020, it's only for 2020 tax returns. To file for 2019 you have to buy TurboTax for 2019, and to file for 2018 you have to buy TurboTax for 2018. You can buy downloads for past years at the following link.
Past Years' Products
Also, there is no "Deluxe home and business." TurboTax Deluxe and TurboTax Home & Business are two different products.
Where did you buy the product that says it's "good back through 2018"? If you did not buy it from a reputable source, I'm wondering if you got something that is not what it claims to be. It might not even be TurboTax at all.
