Permission denied is normal unless you installed Duplicati as a Windows service, running as SYSTEM. Running as you, Duplicati is limited by Windows in the same ways that you are. Restoring to a different location that you actually have permission to write to would prevent errors. Testing restore directly to the original location is somewhat dangerous. If anything goes wrong, you overwrote the original (only) copy.
Backups are easier than proper restores. Many files (such as these) can read by anyone but not written. Other files (such as these) are really system files, and would be better “fixed” with Windows techniques.
Google Drive configuration doesn’t accept --auth-username or --auth-password (as it says). Did you ever configure such things for another storage type that might have leaked over? One somewhat strange case was also just reported where a password manager is believed to have filled out things and caused that…