TL-WR104 3ND? Did you try port forwarding? HiSpeed is right. http://ticket.tp-link.com/index.php?/Tickets/Submit

Your router is WR740N? It has one WAN port and four LAN ports. Maybe there is a sticker covered four LAN ports? Directly connecting to the Ethernet cable from the wall, can you access internet? If...

Try the beta firmware which was mentioned by fotodamaris. :)

Power off the extender and test if you can connect to the main router wirelessly using the same password. If it works, to login web interface of the range extender, you can power off the main router...

Since it's a FTP open on the internet, can you provide the right link? I'll test if I can get the login page. It should help to confirm it is M5350's problem or not.

Phill.ellis wrote Did the LED lights all just go off on the power line adaptor when you first noticed the issue? On one of my adapters the LEDs have all gone off, however the pass through feature...