Can't log in to set up extender as captive.apple.com does not fully load the oage

Help. My extender has suddenly disconnected and I have spent ages trying to reconnect using my iPad.  I have downloaded the Genie app but when it takes me to the logiin it says  Captive.apple.com the Log in underneath and does not load the boxes to enter the passwords. It is a blank page below.

I have tried resetting my network settings as suggested on another forum but captive apple still pops up instead of mywifiext.net. Help! Not the most techno but have always managed to reconnect before after a few attempts