DIAGNOSIS The solid orange Internet LED indicates the router cannot establish a connection to your modem or ISP. The WAN port link is good, but there is no internet data flow.
FIX First, reboot both modem and router. Power off the modem, disconnect its coaxial/RJ45 cable for 30 seconds, reconnect. Power on the modem, wait for its lights to stabilize. Then power on the AX21. If the Internet LED stays orange, log into the router's web interface at tplinkwifi.net. Go to Advanced > Network > Internet. Ensure your Internet Connection Type is set correctly (usually DHCP). Clone your PC's MAC address using the MAC Clone section. Click Save.
IF THAT DIDN'T WORK The issue may be a physical WAN port or cable fault. Connect the modem's Ethernet cable directly to a computer to verify internet works. If it does, try a different Ethernet cable between the modem and the AX21's yellow WAN port. Ensure the cable is fully seated.
HEADS UP Some ISPs bind service to a specific MAC address. Using the MAC Clone function is often required on the first setup. A power cycle sequence (modem first, then router) is mandatory after any physical cable change.