my wifi connection drops when i unplug the ethernet cord from my range extender

Hi, 

i brought a EX6100 AC750 and every time i unplug the ethernet cord that connects the wifi modem to the extender so i can move the extender to another place it drops off and doesnt connect back. 
Ive gone through the configuration process a couple of times and its not doing anything, i have also tried connecting the modem and extender through WPS a couple of times and it doesnt work. I have also tired with the rest button but am sill having no luck 

what can i do to fix this? 

Thanks