I have the same problem, but i couldnt find the answer. Thanks

Please use your phone to connect "TP-LINK_extenderXXX" wifi,then open a web browser,type 192.168.0.254 into the address bar and press enter.

I'm having the same problem. Currently, I can't even see the extender in my WiFi choices... I've reset it and everything. I did have it working a while ago, but for some reason it won't stay synced with the router. When I try and go the 192.168.0.254 it times out. When I try to go to http://tplinkrepeater.net it gives me absolutely no useful information. Becoming less and less impressed with my TP-link products. The amount of time it consumes every couple of months to keep them working is frustrating.

move it a little bit close to your router, range extender should be placed where it can receive good signal from main Wi-Fi.
If you still have troubles, it's suggested to contact TP-link email support..

I was not sure that I had configured the extender correctly, so I wanted to start over. I reset it (pushing recessed button til all lights flash). When I wanted to log in to the web site (either with URL or IP address ) it will no longer let me log in. I hope that someone can help.

you can refer to this for troubleshooting it. http://www.tp-link.com/us/article/?faqid=673