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Troubleshooting Guide: Windows PC Cannot Access NAS via SMB

Applicable Systems: TOS 6, TOS 7

1. Basic Connection Check​

  1. Is the NAS Online?
  • How to Check:
    • Is the NAS powered on?
    • Are the network LEDs functioning normally?
    • Can you access the NAS management page via a browser (using its IP address)?
  • Results and Actions:
    • NAS is offline or the management page is inaccessible → Check the power and network cable connections. Ensure the NAS has started up properly and is on the same local network.
    • NAS management page is accessible → Proceed to the next step.
  1. Is NAS Network Interface Communication Normal?
  • How to Check:
    • Are multiple network interfaces enabled on the NAS?
    • Can all enabled interfaces ping each other successfully?
    • Is the PC accidentally connected to a guest network or a repeater network?
  • Results and Actions:
    • Log in to the NAS management page, go to Control Panel → Network → Interfaces. Ensure both the computer and the NAS are connected to the same router.
    • Check by comparing IP addresses, for example:
      • Computer IP: 192.168.1.10
      • NAS IP: 192.168.1.100
      • If the first three octets are the same (both are 192.168.1) → they are on the same network.
    • If network interface communication is normal → Proceed to the next step to troubleshoot SMB.
  1. Is the SMB Service Enabled?
  • How to Check:
    • Go to Control Panel → File Services → SMB.
    • Check if the SMB service status is "Enabled".
  • Results and Actions:
    • SMB is not enabled → Enable the SMB service and try accessing again.
    • SMB is enabled → Proceed to the next step.

2. Access Address Check​

  1. Is the Access Address Correct?
  • How to Check:
    • Use the correct IP address or device name to access SMB.
    • Windows SMB paths must start with \\ , for example: \\192.168.1.100
    • It is recommended to test using the IP address first to avoid name resolution issues (as names are resolved to IPs).
  • Results and Actions:
    • Neither the IP nor the device name works → Return to the Basic Connection Check and verify network and SMB service status.
    • The IP works, but the device name does not → It is recommended to use the IP address to access the NAS, and restart the Windows PC before trying the device name again.

3. Clear Windows SMB Login Cache​

Issue Description: The local computer may have cached SMB authentication information. If you log in to SMB with a different username or delete the original user on the NAS, it may affect subsequent SMB logins.

Method 1: Delete Windows Credentials​

  1. In the Windows operating system, use the system search function to find and open "Credential Manager" for access and management.

TOSHelp_smb_access_nas_windows_001en.jpg

  1. Locate the credentials related to the NAS IP address, click the dropdown arrow → select "Remove".

TOSHelp_smb_access_nas_windows_002en.png

  1. Check Windows Credentials again to confirm the credentials have been successfully removed.

Method 2: Delete Connected Network Shares​

  1. Press the Windows + R keys to open the "Run" dialog, type cmd and press Enter to open the Command Prompt.

TOSHelp_smb_access_nas_windows_003en.png

  1. View existing network connections by entering:
net use

TOSHelp_smb_access_nas_windows_004en.png

  1. If the list contains \\NAS_IP\IPC$, delete it using the command:
net use \NAS_IP\IPC$ /del

TOSHelp_smb_access_nas_windows_005en.png

  1. Enter net use again to confirm it has been deleted.

TOSHelp_smb_access_nas_windows_006en.png

  • Results and Actions:
    • Credentials cleared → Try accessing SMB again.
    • Access still fails → Proceed to the next step: Protocol and Port Troubleshooting.

4. Check SMB Protocol and Port​

  1. Is the SMB Protocol Compatible?
  • How to Check:
    • Log in to the NAS, go to → Control Panel → File Services → SMB → Advanced Settings, and check:
      • The minimum SMB protocol version
      • Whether SMB transport encryption is enabled

TOSHelp_smb_access_nas_windows_007en.png

  • Results and Actions:
    • SMB protocol version is too low or incompatible → Enable the corresponding SMB protocol based on your Windows version, and increase the SMB version on the NAS.
    • Note: SMB1 has security risks and is only recommended for temporary enabling during troubleshooting or for compatibility with older devices.
    • SMB encryption issues → Temporarily disable SMB encryption to test access (for troubleshooting purposes only).
  1. Is Port 445 Reachable? Delete Connected Network Shares (Note: This heading appears redundant in the original, but is kept for structural consistency. The correct action is the port test below)
  2. Press the Windows + R keys to open the "Run" dialog, type powershell and press Enter to open PowerShell.

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  1. Execute the following command: Test-NetConnection NAS_IP -Port 445
Test-NetConnection 192.168.1.100 -Port 445

TOSHelp_smb_access_nas_windows_009en.png

  1. Check if TcpTestSucceeded is True or False.
  • Results and Actions:

    • Result is True → Port is normal. Continue troubleshooting SMB protocol or permission settings.

    • Result is False → Abnormal. This may be blocked by a firewall or network device. You can temporarily disable the firewall to test access, following the steps below.

      1. In the Windows operating system, use the system search function to find and open "Windows Defender Firewall" for access and management.

      TOSHelp_smb_access_nas_windows_010en.jpg

      1. Click "Turn Windows Defender Firewall on or off", disable it, and then try accessing the NAS again.

      TOSHelp_smb_access_nas_windows_011en.png

      TOSHelp_smb_access_nas_windows_012en.png

  • Results and Actions:

    • Able to access the NAS after disabling the firewall

    • Recommended Actions:

      1. Press Windows + R.
      2. Type: wf.msc, press ENTER to open "Windows Defender Firewall with Advanced Security".

      TOSHelp_smb_access_nas_windows_013en.png

      1. Click "Outbound Rules" on the left.
      2. Click "New Rule..." on the right.

      TOSHelp_smb_access_nas_windows_014en.png

      1. Select Port → Next.
      2. Select TCP, and specify the local port: 445.
      3. Next → Select Allow the connection.
      4. For the network types, only check Private.
      5. Name it, e.g., SMB 445 → Finish.
      6. Try accessing the NAS again.

    • If access still fails after disabling the firewall → Go back and review the previous steps to verify that each step was performed correctly, such as:

    • SMB protocol version

    • SMB encryption

    • Windows credential cache

5. Check NAS Shared Folder Permissions​

  1. Does the User Have Permission for the Shared Folder?
  • How to Check:
    • Go to NAS Control Panel → Shared Folders.
    • Check the read/write permissions of the current user for the target shared folder.
    • If the NAS supports ACL / NTFS permissions, also check those advanced permissions.
  • Results and Actions:
    • Insufficient permissions → Assign read/write permissions and try again.
    • Permissions are correct → Proceed to the next step.

6. Restart​

  • Restart the Windows PC.
  • Reconnect to SMB using \\NAS_IP.