I do hope someone here can help, as this is driving me to distraction!

I want to set up a couple of extenders (AV500 and AV600) from a powerline adapter TL-PA4010. All reset, and firmware updated, I can get them working OK, but I really want a seamless single SSID and password throughout the house. I tried using WPS on the Virgin Super Hub 2, which I can't get to work (apparently it never does), so I need to get in to the WebGUI to sort it..  However, going via http://tplinkrepeater.net, whatever I do, I can't get beyond the page stating:

'Trying to Configure the Range Extender?

It looks like you may have run into an issue'

and giving various options, non of which I can get to work: I am definitely running from the extender in question, not directly from the Virgin router, either via wifi on my 'phone, ipad, or ethernet on my Mac and a PC; I've tried all the different browsers, all ending up at the error page!

And I can't work out what I need to do for the final instruction:

' By LAN IP: go to the DHCP Client List on your router, check the range extender’s current IP and type it in the address bar.'

If I look on my Mac at the wifi preferences, the 'client list' is blank..

I'd so appreciate it if anyone can tell me how to get in to alter the SSID and password!

Thanks in advance.