j4335dw won't connect to wifi anymore after a router change, can't even find it in the wireless setup

Diagnosis

The Brother MFC-J4335DW is designed to "lock" onto a specific Service Set Identifier (SSID) and security key. When you replace a router, the printer continues to attempt a handshake with the old credentials. Because the hardware is still actively searching for the previous network, it often fails to enter "Discovery Mode," making it invisible to your new router and mobile devices during a standard wireless scan. Furthermore, this specific model is sensitive to frequency bands. Most new routers use "Smart Connect" or "Band Steering" to merge 2.4GHz and 5GHz bands into one name. The MFC-J4335DW occasionally struggles to handshake with 5GHz-dominant signals during the initial setup phase, leading to the "Network Not Found" error or the printer simply not appearing in the available networks list. To confirm this is a credential lock, check the LCD screen; if it shows "Offline" or a wireless icon with a red 'X', the printer is stuck in a loop trying to reach a non-existent gateway.

How to Fix It

Since the printer is not appearing in the wireless setup, you must force a network reset to clear the old cache and trigger the broadcast signal. Follow these exact steps:

1. Press the Settings (wrench/screwdriver icon) button on the touch screen.
2. Navigate to All Settings and scroll down to Network.
3. Select Network Reset. Confirm by selecting Yes. The printer will perform a soft reboot of the wireless card.
4. Once the reset is complete, return to the Network menu and select WLAN.
5. Choose Setup Wizard. The printer will now scan for all available SSIDs in the vicinity.
6. Select your new network name from the list. If you have a dual-band router, ensure you are selecting the 2.4GHz band if the 5GHz option is not appearing.
7. When prompted for the password, use the on-screen keyboard to enter your WPA2/WPA3 key. Note that this is case-sensitive; use the shift key for capitals.
8. Once the "Connected" message appears, print a Network Configuration Report from the Network menu to verify the IP address is assigned correctly (e.g., 192.168.1.X).

If That Didn't Work

• Disable 5GHz Band Steering: Log into your router's admin panel (usually 192.168.0.1 or 192.168.1.1) and temporarily disable "Smart Connect." Give your 2.4GHz and 5GHz networks different names (e.g., "Home_Wifi" and "Home_Wifi_5G"). Connect the printer specifically to the 2.4GHz band, as it provides a more stable long-range connection for inkvestment printers.
• Manual IP Assignment: If the printer connects but the computer can't find it, the DHCP handshake failed. Go to Network → WLAN → TCP/IP on the printer. Change the Boot Method from Auto to Manual. Assign a static IP address outside your router's typical DHCP range (e.g., if your router starts at .2, set the printer to .200) to prevent IP conflicts.
• WPS Push Button Method: If the Setup Wizard fails, go to Network → WLAN → WPS. Select Push Button. Within two minutes, press the physical WPS button on your router. This bypasses the SSID search and forces a direct hardware handshake.
• Hard Power Cycle: Unplug the power cord from the back of the MFC-J4335DW and remove the battery (if applicable) or simply leave it unplugged for 60 seconds. This clears the volatile memory (RAM) of the network interface card, which sometimes holds onto "ghost" settings from the previous router.

Heads Up

• Avoid USB-to-Wireless Bridges: While using a USB cable for setup is possible, it often creates a "dual-homed" configuration that confuses the Brother print spooler on Windows 10/11. Always prefer the on-device Setup Wizard for the cleanest connection.
• Security Protocol: Ensure your router is not set to "WPA3-Only." The MFC-J4335DW works best with "WPA2-AES" or "WPA2/WPA3 Mixed Mode." Pure WPA3 often results in a "Connection Failed" message during the final handshake.
• Firmware Updates: Once connected, immediately check for firmware updates via the Machine Info → Firmware Update menu. Brother frequently releases patches specifically to improve compatibility with newer WiFi 6 routers.
• Sleep Mode Latency: This model can enter a "Deep Sleep" where the WiFi radio powers down. If you find the printer frequently goes offline, disable "Deep Sleep" in the General Settings to keep the network heartbeat active.