Check local area connection on your PC. Ensure it is using DHCP and IP address, default gateway etc. are obtained automatically...

Thanks for your comment. I have checked all the configures and regarding DHCP it is not enabled. Since I using Static IP connection type I have configured manually with IP address, default gateway, DNS server etc. But when I want to obtain it automatically it shows limited or no connection and I could not connect to internet. Please help
With regards

A.D.

Try a different computer or different ethernet cables. If none of them can obtain correct IP address automatically, it should be a faulty unit.
http://www.tp-link.in/support/rma/

Thanks a lot. I have tried it with different computer and it works well. But a problem has been arisen when I connect my computer with its lan it appears that download speed from any torrent site is terribly slow it may be maximum 30kbps. It happen with wifi mode also. But when I connect my pc directly without router the speed increased to 3mbps to 5 mbps. It may be mentioned here I am tried same file with same seed etc. but result is same. I don't why it happen is it router problem or I have to do some configure in this issue. Please help.

Check hardware version and firmware verison of your WR841N. If there is an update, upgrade the latest firmware. Reset and reconfigure it to check if there is any improvement. Provide screenshots of your tests pls.
http://www.tp-link.com/en/download/TL-WR841N_V10.html