Getting EX6400 to work with Verizon Fios G3100

Hi all,

I have Wifi extender EX6400. Worked well with out previous Verizon Fios Router. Then we upgraded our speed to 200/200 and the router to G3100, and have been unable to setup the extender since. Every time we do, it brings down both existing and new network and we completely lose Wifi. Tried setting it up multiple times, each time resetting it, followed by setup through wifi, or through WPS, or with direct connection to router. Added EX6400's MAC in the router's admin site, to be allowed access. Nothing works and it's super frustrating. Any idea? FYI - when going through the setup genie, it keeps insisting on 'finding' 2.4ghz & 5ghz networks, though there's only one wifi network (unless one sets up a guest network). 

Any input would be greatly appreciated.

Thanks!

Shiri