I received the error message "System error 53 has occurred. The network path was not found." when connecting to Synology NAS via SMB. What can I do?

Symptoms

Windows displays the error message, "System error 53 has occurred. The network path was not found." when connecting to a shared folder on Synology NAS using Synology Assistant via SMB or when using a net use command.

Resolution

Make sure that the client computer can reach your Synology NAS if they are located in the same LAN:

You can run a "ping" command to check the overall connectivity. Open a Command Prompt window and enter "ping" followed by the IP address of your Synology NAS.¹²

Make sure that the Client for Microsoft Networks is enabled on your Windows client's Ethernet adapter:

The GUI options in this section only apply to Windows 10. Older versions of Windows may use different option names.

Go to Start > Settings > Network & Internet > Change adapter options.
Select a network and click Organize > Properties.
Make sure that the Client for Microsoft Networks checkbox is ticked.
Click OK.

Make sure that the group policy Network Security: Restrict NTLM: Outgoing NTLM traffic to remote servers is not set to "Deny All":

If the computer is for personal use, check the policy in Local Group Policy Editor by following the steps below.³

Open Command Prompt or Windows PowerShell.
Enter "gpedit.msc" to launch the Local Group Policy Editor.
Navigate to Computer Configuration > Windows Settings > Security Settings > Local Policies > Security Options > Network security.
Find Restrict NTLM: Outgoing NTLM traffic to remote servers and make sure it is not set to Deny All.

If the computer is managed by group policies in a Windows domain, check the group policies in Group Policy Management Editor by following the steps below.

Go to the domain controller and open Command Prompt or Windows PowerShell.
Enter "gpmc.msc" to launch Group Policy Management.
Expand the Forest and Domains nodes to select a domain.
Expand Group Policy Objects for the domain.
Select an existing group policy object, such as Default Domain Policy, then right‑click and select Edit.

Navigate to Computer Configuration > Policies > Windows Settings > Security Settings > Local Policies > Security Options > Network security.
Find Restrict NTLM: Outgoing NTLM traffic to remote servers and make sure it is not set to Deny All.

If you encounter the error when using a net use command:

Try closing all File Explorer windows and run net use * /d /y in Command Prompt. Then, try connecting to a shared folder with the net use command (e.g., net use z: \\192.168.xxx.xxx\ShareFolder) again.
Try connecting the client computer to a Windows file server. If the error remains, it suggests that the problem is with the client computer. In this case, you will need to contact the system administrator or Microsoft for further assistance.

Notes:

Ping is a network utility that sends an echo request packet to an IP address and then waits for a reply. A successful ping gets a reply from the server. Ideally, no packets should be lost and the approximate time taken per round trip should be short.
If you cannot get a reply from your Synology NAS, or the client computer and Synology NAS are not located in the same LAN, please check with your network administrator for potential network issues.
The Local Group Policy Editor is not available in Windows Home edition, but available in Windows Professional/Enterprise editions.

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