In Windows 10, version 1709, Windows Server version 1709, and Windows Server 2019, the SMB2 client no longer allows the following actions:
Guest account access to a remote server
Fallback to the Guest account after invalid credentials are provided
see https://support.microsoft.com/en-us/hel ... indows-ser
Solution: Run "gpedit.msc", then navigate to Computer Configuration\Administrative Templates\Network\Lanman Workstation and set Enable insecure guest logons to Enabled