I've seen this issue every single year since the release of Windows 10. This is caused by a Windows 10 setting and has nothing to do with the TurboTax program. The fix is not intuitive, but it is simple, *if* you know how.
Click Start, then the Settings icon (the little gear wheel) to open the Windows Settings applet.
In the search box enter "Controlled Folder Access" (without the quotation marks) and press the enter key on your keyboard.
In the search results window click on "Controlled Folder Access". This opens the "Ransomeware Protection" applet.
First item listed is "Controlled Folder Access". You can turn it off, which I don't recommend, or configure it to allow TurboTax to save to the default location as designed and intended. To configure it:
Click "Allow an app through controlled folder access"
Select "Add an allowed app" followed by "recently blocked apps"
Select the TurboTax program and then OK out of everything.
That does it.
