How to fix Mac that cannot connect to or mount a network shared drive (SMB) on macOS

Summary

This guide helps you troubleshoot and resolve: How to fix Mac that cannot connect to or mount a network shared drive (SMB) on macOS. Follow the steps below to fix the issue.

Common Causes

Connecting your Mac to a network shared drive using SMB (Server Message Block) is usually straightforward, but occasionally macOS can refuse to connect or fail to mount the share. This guide walks you through the most common causes and provides step-by-step fixes to get your Mac talking to your Windows server, NAS device, or other SMB share again.

Quick Fix Steps

If you're in a hurry, try these steps in order. Most SMB connection issues are resolved by the first few items on this list.

1. Confirm the share is online and reachable from another device on the same network.
2. Verify you are using the correct username, password, and share path.
3. Restart your Mac and the device hosting the share.
4. Connect using smb:// in the Connect to Server dialog.
5. Sign out of iCloud Drive or disable Optimise Mac Storage if the share is hosted via iCloud.
6. Reset your Mac's keychain entry for the share.

Detailed Instructions

1. Confirm the Share Is Reachable

Before changing settings on your Mac, rule out a network or server issue.

• Ping the server from your Mac by opening Terminal (found in Applications > Utilities) and typing ping -c 4 servername.local or ping -c 4 192.168.1.10 (replace with your server's address).
• Try connecting from another computer or device on the same network.
• Confirm the server, NAS, or PC hosting the share is powered on and not in sleep mode.

2. Connect Using the Correct Protocol and Path

macOS uses different protocols depending on the share type. For Windows shares and most NAS devices, use SMB.

1. Open Finder.
2. From the menu bar, choose Go > Connect to Server (or press Command + K).
3. In the Server Address field, enter the address using the SMB protocol. For example:
   • smb://nas.local/sharedfolder
   • smb://192.168.1.50/data
   • smb://server.example.com/team
4. Click Connect.
5. When prompted, enter the username and password for the share. If the share allows guest access, choose Guest.

3. Sign In With the Correct Credentials

SMB authentication can be picky about how usernames are formatted.

• For a local account on a Windows PC or NAS, use just the username (for example, john).
• For a Windows domain account, use the format DOMAIN\username or [email protected].
• For a Microsoft account, use your full email address.
• Ensure CAPS LOCK is off and that you are not accidentally entering a saved password from another service.

4. Restart Your Mac and the Server

A simple restart clears stale network connections and resets background services that may be blocking the SMB session.

1. Save any open work and choose Apple menu > Restart.
2. Restart the device hosting the share (NAS, Windows PC, or server).
3. Once both devices are back online, try connecting again using Go > Connect to Server.

5. Remove and Re-add the Share From Keychain

macOS stores SMB credentials in Keychain Access. If the password has changed or the saved entry is corrupt, your Mac will keep failing to authenticate.

1. Open Applications > Utilities > Keychain Access.
2. In the search field, type the server name or IP address (for example, nas.local).
3. Select any matching entries and press the Delete key, then confirm.
4. Quit Keychain Access and try connecting to the share again. You will be prompted to enter the password fresh.

6. Check macOS Sharing and Firewall Settings

If your Mac is hosting the share, or if a local firewall is blocking outbound SMB traffic, the connection will fail.

1. Open System Settings > General > Sharing.
2. Ensure File Sharing is turned on if you intend to share folders from this Mac.
3. Open System Settings > Network > Firewall and confirm the firewall is not blocking smbd or incoming connections on ports 445 and 139.
4. If you use a third-party security app (such as Little Snitch or Lulu), check that SMB traffic to your server's IP address is allowed.

7. Force SMB Signing or Disable If Required

Some older NAS devices and Windows servers do not support modern SMB signing requirements. macOS may refuse to connect if the signing negotiation fails.

1. Open Terminal from Applications > Utilities.
2. To check the current signing policy, type: sudo defaults read /Library/Preferences/nsmb.conf (you may be prompted for your Mac password).
3. If no file exists, you can create one to relax signing. Type:
   • sudo nano /etc/nsmb.conf
4. Add the following lines:
   • [default]
   • signing_required=no
   • validate_neg=no
5. Press Control + O to save, then Control + X to exit.
6. Restart your Mac and try connecting again.

8. Mount the Share Automatically at Login

Once the connection works, you can make macOS reconnect to the share every time you log in.

1. In Finder, connect to the share using Go > Connect to Server.
2. Once mounted, open System Settings > General > Login Items.
3. Under Open at Login, click the plus icon and add the mounted share from the list.
4. Tick Hide if you do not want a Finder window to open each time.

Troubleshooting

"There was a problem connecting to the server"

This generic error usually indicates the server is unreachable, the share name is wrong, or the SMB service is not running. Verify the server's IP address with ping and confirm port 445 is open by typing nc -zv servername 445 in Terminal.

"You entered an invalid username or password"

The credentials are being rejected by the server. Remove the saved entry from Keychain Access as described in step 5, then re-enter the username in the correct format for your server type.

Share mounts but folders appear empty

This is typically a permissions issue on the server side. Confirm that the user account has read or write access to the share and that any NTFS or filesystem permissions allow access.

Connection works on Wi-Fi but not Ethernet (or vice versa)

macOS may be treating the networks differently. Open System Settings > Network, click the network interface in question, then set Configure IPv6 to Link-local only or Off if your network does not use IPv6.

macOS Sonoma or later prompts for keychain password repeatedly

Apple introduced stricter keychain handling in recent versions of macOS. Open Keychain Access, locate the entries for your SMB server, delete them, then reconnect to the share and choose Always Allow when prompted to update the keychain entry.

Connection drops or is slow after macOS update

Major macOS updates can reset network settings and clear saved SMB credentials. Repeat steps 4 and 5 above, and if the issue persists, remove the /etc/nsmb.conf file (if you created one) and re-add your share.

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