There is no TurboTax download software that will run on a Chromebook. You have to either use the Windows download on a Windows computer, or the Mac download on a Mac. Your problem isn't accessing your download. Your problem is that you bought the Windows download but you are not installing it on a Windows computer. Downloading it again isn't going to change anything.
If you don't have a Windows computer, and your Mac meets the system requirements for the Mac software, ask customer service to exchange your Windows download for a Mac download.
Critter-3 posted a link for the Mac system requirements in the first reply in this thread, above.
