EX6200 lost connection now can't reinstall?

I have been using this unit for over a year with only 1 issue (similar to this that took days to resolve and I didnt do anything in particular to resolve).  I use a mac book pro OSX 10.9.5.  My modem/router is a standard telstra bigpond technicolour TG587n v3.  I can only connect to the 2GHZ range as this doesnt have 5 GHZ (even though this always shows up under my WIFI networks.  Originally this was installed no problem (picked up straight away).  Recently it dissapeared from my Wifi List (2GHZ - it still displayed 5GHZ even though this doesnt work).  After a few days of it not being available I decided to do what I do previously and reinstall. After resetting modem, extender, computer etc and attempting to connect via your instructions using WPS I had no luck.  Two things I noticed with this and not sure if it is normal.  1) when I press WPS on modem - no lights come up and 2) after the flashing green lights on extender it stays solid green for quite a few seconds and then all lights out (except power NETGEAR sign still lit up).  So I then proceeded to connect via your manual configuration steps.  However I cannot see the NETGEAR option under WIFI at all.  I have made sure i am not connected to a network when connecting as from memory one of these options suggested that but still no luck.  Numerous resets on both devices and still no luck.  Please help!  Thanks