N300 Wifi extender not connecting

I am trying to set up a new wifi extender, but its not connecting. The power is on and I have a working internet connection, but I can get the router link or the client link to turn on. For internet access I use a modem from AT&T U-Verse

When I try and set up using a browser set up http://mywifiext.net/ I get this message YOU ARE NOT CONNECTED TO YOUR EXTENDER’S WIFI NETWORK. PLEASE CHECK YOUR CURRENT CONNECTION AND TRY AGAIN

PLEASE HELP!