Netgear extender AC750 Model EX6000 unable to accept wifi password when connecting to extender

Hi all,

Hoping someone can advise what to do here. I have a Netgear AC750 Model EX6000 wifi range extender. I believe I have initially set up the extender correctly as the power / Router & wps/mode LEDs are solid green lights.

However, when I try to connect an Android phone (Galaxy s8+) when I enter the wifi router code (using the <router address>_2GEXT (_5GEXT) it is saying that I have entered the incorrect password, when in actual fact it is the correct code for the router as the pc is also connected on the same passcode. Please advise what I can do or if the extender is compatible or not with what I'm trying to use it for. 

Any help gratefully accepted.

Thanks

Graham571