Did you install the driver or just plug it in? Operating System of your PC? Model number of the PC's motherboard? It looks like a compatibility issue.

All except nettalk are working, right? You should contact nettalk instead of your ISP... Any configuration has to be done to make nettalk work? Do you remember it?

Place them in the same room or same extension cord. Press pair button on one for 10s. And then, there are two ways to pair them again. With powerline lights on, connect them back and try internet...

I don't think there is an update in their database...Did you check on their website?

Follow this guide to try. http://www.tp-link.us/article/?faqid=381

It is an annoying issue. Report it here for a solution. http://ticket.tp-link.com/index.php?/Tickets/Submit