trying to scan to my computer over wifi and it just fails every time, connection seems fine

Diagnosis

The failure of the scan function on the Brother DCP-L2640DW, while printing still works, is a classic symptom of a "half-connection." Printing uses a different protocol (typically TCP/IP port 9100) than scanning (which relies on TWAIN or WIA drivers and specific UDP ports). When the printer reports a "Connection Failed" or "Unable to scan" error, it is rarely a problem with your Wi-Fi signal strength, but rather a communication breakdown between the Brother ControlCenter4 software and the printer's network IP address.

This most commonly happens after a Windows Update or a router reboot that assigns the printer a new dynamic IP address. Because the Brother scanning utility is hard-coded to look for the printer at a specific IP (e.g., 192.168.1.15), if the printer shifts to 192.168.1.20, the scan command will time out and fail, even though the "Print" command—which is more flexible—continues to work. Additionally, Windows Defender or third-party firewalls often block the specific ports required for the "Scan to PC" handshake, treating the incoming scan data as an unauthorized network intrusion.

How to Fix It

To resolve this, you must reset the communication bridge between the DCP-L2640DW and your PC. Follow these exact steps:

1. Open the Control Panel > Programs and Features and uninstall "Brother MFL-Pro Suite" and any "Brother Scanner Driver" entries. Restart your computer to clear the registry cache.
2. On the printer's physical touch panel, press Menu > Network > TCP/IP > IP Address. Write down the current IP address displayed (e.g., 192.168.1.XX).
3. Download the Full Driver & Software Package from the Brother support site. During installation, when prompted for the connection type, select Wireless Network Connection.
4. If the installer does not find the printer automatically, select "Specify the IP Address" and enter the exact digits you wrote down from the printer's screen.
5. Once installed, open Brother ControlCenter4. Go to Configuration > Scan-to-PC and ensure the "Scan" checkbox is enabled.
6. Run the Network Connection Repair Tool (found in the Brother Utilities folder in your Start Menu) to synchronize the PC's port settings with the printer's current IP.

If That Didn't Work

• Assign a Static IP: Access your router's DHCP settings and create a "DHCP Reservation" for the printer's MAC address. This prevents the IP from changing in the future, which is the primary cause of recurring scan failures.
• Adjust Firewall Rules: Open Windows Defender Firewall > Allow an app or feature through Windows Firewall. Ensure that "Brother ControlCenter4" and "BrScan" are checked for both "Private" and "Public" networks. If using Norton or McAfee, manually whitelist the printer's IP address.
• Disable " SNMP" Status: Go to Devices and Printers > Right-click Brother DCP-L2640DW > Printer Properties > Ports > Configure Port. Uncheck the box that says "SNMP Status Enabled." This often removes the "Offline" ghosting that prevents scanning.
• Test via Web Interface: Type the printer's IP address directly into a web browser. If the printer's web page loads but the scan still fails, the issue is 100% software/driver-related on the PC, not a hardware or network failure.

Heads Up

• Avoid "Generic" Drivers: Never rely on the drivers Windows automatically installs via "Plug and Play." These allow printing but almost always lack the TWAIN drivers necessary for scanning.
• Avoid 5GHz Bands: If your router has separate 2.4GHz and 5GHz bands, ensure the printer is on 2.4GHz. Laser printers often have stability issues with 5GHz bands over long distances.
• Sleep Mode: If the printer is in "Deep Sleep," the first scan attempt may fail. Press the "Home" button to wake the machine before initiating a scan from the PC.
• USB Fallback: If wireless scanning continues to fail during a critical task, the DCP-L2640DW supports a direct USB-B connection which bypasses all network and firewall hurdles.