Hello @Jaygujrati 

1. Please verify the Wi-Fi password of the main router before RE set up: 

Log in to the management page of your router if possible, double-check the Wi-Fi password. Or forget router Wi-Fi network on mobile device  temporarily , connect back to router Wi-Fi by putting in password manually to examine WiFi password.
 FAQ: How to remove existing wireless network profile on Android&iPhone

2, Later try factory reset extender and install it from scratch: 
RESET: With the extender powered on, use a pin to press the RESET button until most Leds flash once. 
Later, please follow the instructions here to set up range extender :

How to configure Range Extender via Tether APP

How to configure my range extender via web GUI to extend an existing wireless network's coverage (new logo)?

Did you verify main router WiFI password is correct, how about the Led status now on RE after set up? Thank you.