Kitchu, are you using TP-LINK modem to replace BSNL modem? From your description, it seems that it is a synchronization issue. Is it ADSL2+ line or something else? Try to change DSL mode to ADSL2+ on...

For TD-W8970: Network---DSL Settings---DSL Modulation Type Change the type to ADSL2+ and Save. Wait for 2 minutes and check upstream and downstream again.

mrmima has tried already. Read this, http://forum.tp-link.com/showthread.php?78473-TL-WR740N-and-Sony-Xperia-Z1&region=china.

If you restart it, you can login, right?

The adapter is installed on the TV? When network is secured, did you type in the password to connect Wi-Fi? Any error message? You should intall the adapter on a PC to test.

@Kyrne Model number of your router? Firmware version of your WA850RE? Status page and system log screenshot pls.