If a user is unable to log in to the Tplinkwifi.net interface, the first thing you need to make sure of is that the router must be connected to the Tp-link range extender. Ensure that the range extender is not connected to other wireless networks and stop other web applications too that are running on the computer. If a device has been connected to other wireless networks it becomes difficult for the computer to interact with the web management window of a Tp-link range extender.