Hard reset TP-LINK TL-WR841HP

Factory reset (Hard reset) Power ON the router. Locate the WPS/RESET button on the back panel of the device. Press and hold the button for more than 5 seconds. Keep an eye on the system LED and when it starts flashing more quickly than before – release. Wait for the router to reboot.  
PS. The system LED is the second led on the front panel – it is right next to the power LED.
Firmware Firmware link
Default username admin
Default password admin
Default IP address