The status of the filed 2019 tax return is not relevant for you being able to file a prior year tax return.
To complete a 2018 and 2017 tax return using TurboTax you will need to purchase, download and install on a personal computer one of the 2018 and 2017 desktop editions from this website - https://turbotax.intuit.com/personal-taxes/past-years-products/
A 2018 and 2017 tax return can only be printed and mailed, they cannot be e-filed.