It is good to know that it works now anyway...

If you remove the POE injector, it will work again? I cannot figure out what's wrong there...What's the IP address of your W8960N and WA901ND?

If you can ping 8.8.8.8 but google.com, it should be DNS issue. On DHCP Server---DHCP Settins page, change primary DNS to 8.8.8.8 and Save to see if it works.

On web interface of D2---Status page, there is WAN IP address? Go to Diagnostic and test internet browsing. What does it show? When you try to open a webpage, what's the error message? Can you ping...

I tried my best... Ask TP-LINK technician to check your settings.

Upgrade the latest firmware for the WA901, reset and reconfigure it. http://www.tp-link.com/en/download/T....html#Firmware If the problem continues, try to replace it under warranty.