Thanks Verbitan & Bodski. I think the logic behind this is that the main router which uses 3-add WDS mode won't talk properly with the TL-WR702N client which uses 4-add WDS mode. So the problem is...

It seems that only when the router works in "AP Client Router" mode, you can configure a separate SSID.

Give a try as http://www.tp-link.com/en/article/?faqid=376.

Do you get WAN details on the router's status screen? Is the WAN IP address there 0.0.0.0? If you have WAN details, then go to system tools, diagnostic, and ping 8.8.8.8 there and see if you can ping...

Thanks Notorious. TPLINK must be working on tthis issue. We may let it go and give TPLINK some time for a fix. Once you get the fix from tplink, please share with us...:D

In your case, you can connect your 1st router from LAN port to WAN port on TL-WR740N, configure "static IP" as TL-WR740N's WAN Connection Type, and enter all the required WAN details, like the IP...