@Amer-Hash 

Hi,

In case you have "Band Steering" activated in the Wireless Settings menu of the NX200 switch it off and then try again if the RE305 can connect as EasyMesh device.

Edit: If the above by itself doesn't help also try to connect the two devices using the WPS method. (i.e. first press the WPS button of the NX200 and right after that press the WPS button of the RE305)

Hi  @Amer-Hash 

As woozle said, you can try WPS buttons to create easymesh network between NX200 and RE305.

It is recommended that you can factory reset the RE305 before you set up easymesh network:

Keep power on, Use a pin to press the reset button(hole) for 1 second to reset the extender