DIAGNOSIS Your computer or phone is no longer on the same network segment as the router's management interface. This usually happens if you've changed the router's IP address, enabled AP (Access Point) mode, or your device is connected to a different network (like a guest network or a different router).
FIX Ensure your device is connected to the AXE75's Wi-Fi network (any band). Open a command prompt (Windows) or terminal (Mac) and type 'ipconfig' or 'ifconfig'. Look for the 'Default Gateway' address. That's your router's current IP address—it might not be 192.168.1.1 anymore. Try typing that new gateway IP directly into your browser's address bar.
IF THAT DIDN'T WORK The router might be in AP mode. Check the physical mode switch on the side of the router. If it's set to 'AP' (Access Point), the management IP is handed out by your main router. You'll need to find the AXE75's IP from your main router's client list, or switch the mode back to 'Router' temporarily to access settings at the default IP.
HEADS UP Some browsers or ad-blockers cache the old address hard. Try a different browser, use incognito mode, or clear your browser cache. Also, make sure you're not typing 'www.tplinkwifi.net'—it's just 'tplinkwifi.net'.