Troubleshooting a TP-LINK router is dependent on the actual problem and the model of the router. Common problems include loose cable connections, dysfunctional indicator lights and low data rates.
Check for loose connections between the power adapter cable and the wall socket. Damaged power adapters cannot transmit power to the router. Ensure the Ethernet cable goes from your computer to the LAN port on the router properly. Check also for proper telephone line connections between the modem's LINE port and the filter's modem port.
Dysfunctional Power and ADSL lights point to power adapter and modem problems, respectively. This could be the result of loose connections or damaged cables and devices. When Internet indicator lights are off, check whether the username and password details are correct. Also, deactivate any filter rules in the router's configuration to ascertain they are not limiting Internet connectivity. Check for loose or damaged cables when the LAN lights are off.
Check for damaged or loose connections between the modem router and wall jacks, which could cause the Data Rate value to show N/A. This value indicates that the modem router is not synchronized with your ISP. Change any damaged cables and also ensure the Data Rate values go hand in hand with those provided by your ISP.