Can't Connect my Wifi Extender to computer through WPS

I got a N300 extender recently and set it up to work through WPS, using my Virgin Superhub 2 router. 

I have connected the extender to the router through WPS (both WPS and Router lights are solid green), the **********_EXT shows up in my list of Wifi networks, but I cannot connect to it with any of three devices (PC in living room near router, Laptop in loft and mobile phone). The PC and phone both ask for password, I enter the normal router password and I get the message 'unable to connect to this network', no prompt for password on Laptop, but just get same message. 

What am I doing wrong?