I am facing the exact issue as mentioned in PowerShell ProtectedData.Unprotect Fails in Console but Works in ISE.
I am able to protect/unprotect in powershell ISE but when I try the same script in powershell console, I get the following error during unprotect: Exception calling “Unprotect” with “3” argument(s): “The operation completed successfully. Any help with this will be appreciated.