@Satheesh_85 

Theoretically, what you reported won't happen but we will check some details if it is true:

1. When there is a power outage then back on, are you still able to access the web UI of the WR841N, and what is the IP address of it? Did you change its IP to be in the same IP subnet as the main router?

2. What is the model number of your main router? Will it be correctly on and connect to the internet correctly after the power outage?

3. Please reset the WR8410N and ensure its firmware is the latest, then try to configure the WDS settings again:

How to configure WDS function on TP-Link Wireless Routers

May it helps.

@Kevin_Z 

Thanks for the feedback. Please find my reply below.

1) I am not able to access the router at all after power on. My main routers IP is 192.168.0.1 and I changed the IP address second router to 192.168.0.10. The secondary router is not accessible at all with the changed IP and I will have to do a factory reset and start configuring again from beginning.

Main router ip - 192.168.0.1

Secondary router ip - 192.168.0.10

2) The primary router (Tenda) is fine after power ON and it is connected to the internet. Only the secondary router is loosing its configuration and IP after power ON

3) Firmware update is also done but still the problem exists. Every time after power ON, I will have to reconfigure the IP and WDS settings. I have followed the same steps mentioned in the link