Windows 2019 blocks unauthenticated guest access. If mounting a CSG SMB share fails with a guest-access security policy error, enable the Enable insecure guest logons Group Policy setting to restore access.
Symptoms
Mapping a network drive to an SMB share — for example, \\172.16.0.110\cifs0617 — fails with the following error:
You can't access this shared folder because your organization's security policies block unauthenticated guest access. These policies help protect your PC from unsafe or malicious devices on the network.
Solution
Press
Win+Rto open the Run dialog box. Entergpedit.mscand click OK.In the left-side navigation pane of the Local Group Policy Editor, navigate to Computer Configuration > Administrative Templates > Network > Lanman Workstation.
On the Lanman Workstation page, in the Setting section, double-click Enable insecure guest logons.
In the Enable insecure guest logons dialog box, select Enabled and click Apply.
Mount the SMB share again.
If the SMB share is still inaccessible, restart the Windows client to clear the cache, then mount the share again.