The problem is caused by a new security feature in the latest (and future) updates to Windows 10 called Controlled Folder Access. The feature is intended to protect against ransomware and other threats. To distinguish the difference between legitimate programs and malware, the user is required to provide a list of exceptions. In the absence of an exception, access will be blocked.
The solution is to either make TurboTax an allowed program or to turn the feature off completely.
Settings can be found in Windows 10 at: StartMenu, Settings, WindowsSecurity, VirusAndThreatProtection, VirusAndThreatProtectionSettings, ManageControlledFolderAccess
Problem solved.
-bs
