DIAGNOSIS Your computer is not on the same network segment as the router's default gateway. This is a local IP configuration or physical connection problem.
FIX Ensure your PC is connected via Ethernet to one of the router's LAN ports (yellow). Open Command Prompt (Windows) or Terminal (Mac). Type 'ipconfig' or 'ifconfig'. Look for the Ethernet adapter's Default Gateway. It should be 192.168.0.1 or 192.168.1.1. Type that IP address directly into your browser's address bar, not the search bar. Use http://, not https://. The setup page should load.
IF THAT DIDN'T WORK Your network adapter may have a static IP conflict. Set your PC's Ethernet adapter to obtain IP and DNS automatically (DHCP). For Windows, go to Network Connections > Adapter Properties > Internet Protocol Version 4 (TCP/IPv4) > Obtain an IP address automatically.
HEADS UP The tplinkwifi.net domain relies on your router's DNS. If your PC is using a static DNS like 8.8.8.8, the domain will not resolve. Always use the router's default gateway IP for initial configuration. Disable any VPN or proxy during setup.