If you take adapter B back to the same room as adapter A, how about status of powerline light(middle one)? If they are not on, try to pair them again.
But you may have to reset them with the utility if nothing changes during pairing process.
http://www.tp-link.com/en/faq-312.html
Later test if they work in different rooms. It should be wiring issue if they won't work in different rooms but in the same room they can be paired.

Thanks. I'll try.