I too am having trouble. First, I cannot find the 2018 software on that link and second, all my activations license codes for 2015 thru 2017 do not seem to work. Yet, from 2019 onwards they do?
I had a similar issue to the original poster -- hard drive failure necessitated I rebuild the PC and needed to reinstall TurboTax. I have the install CDs but they won't activate as the server they are trying to access seems inaccessible by any software prior to 2019 and I need to have at least seven years so that is back to 2016 but ideally, 2015 as a minimum (for carry forwards etc.)
Help appreciated.
