I am facing a problem with configuring my WiFi Range Extender with the base router.. I tried to find a solution through many forums, but nothing worked... any help is highly appreciated.

I have a Netgear WNDR-3700v1 router (Atheros AR7161) installed with OpenWRT 18.06.2 as my base router, which is connected to my cable modem. Its working perfectly fine with my laptops and mobiles when connected directly through Lan Cable or WiFi. 

I have a TP-Link TL-WA855RE v4 Wi-Fi Range Extender in my living room, which is connected to this Netgear base router.

But the Range Extender was not identifying internet. In one of the forums, I found a solution to this - to disable DHCP in the TP Link Range Extender. With the DHCP disabled in the TP-Link Range Extender, I am able to connect my laptops to the network and connect to internet as well. I get the base routers DHCP IPs on the laptops also.  

But my Android mobile devices are not getting the IP address when connected through the Range Extender. I tried almost all permutations of the settings in the Range Extender, but nothing worked.

If I set static IP address for my mobile device, the connectivity through the Range Extender also works fine... In DHCP mode in mobile devices, they are failing to get the IP addresses if connected through the TP-Link TL-WA855RE v4 Wi-Fi Range Extender (with DHCP off) to my base router running OpenWRT. 

Please help me with a solution.