You got only 2 signal lights? If so, you should place the extender closer to the main router and ensure you get at lease three signal lights to ensure a stable connection. By the way, check the...

Can you provide a screenshot of configuration on web interface of WR841ND?

Did you read this FAQ? http://www.tp-link.com/en/faq-445.html

It is slow but you can access internet, right? Did you install powerline utility? What's the rate? Are they brand new? You may try to reset them and re-pair. http://www.tp-link.com/en/faq-312.html...

They are compatible with each other. Pairing method: http://www.tp-link.com/en/faq-258.html

the one connected to the computer won't get Ethernet and I can't find the device via the utility program How about status of Ethernet light? Can you access internet? Did you try to install the...