I am having the same issue. I have used the same machine for years to do my taxes with TurboTax, and there has never been a problem. The stated RAM requirements for the 2019 and 2020 versions are identical, yet I am unable to install the 2020 version.
[Comment edited to reflect the TurboTax representative's helpful comments on how to apply for a refund if forced to switch to TurboTax Online.]
