Did you try to hard reset it? If nothing change, it should be a faulty unit...

Did you enable remote management on System Tools---Manage Control page? Provide a screenshot of your configuration.

What's the hardware version of your W8968? Its firmware is up to date? http://www.tp-link.com/en/download/TD-W8968_V3.html ADSL LED is always on? Provide screenshot of status page and system log....

Try to install the driver manually. http://www.tp-link.com/en/faq-228.html The driver can be copied from the disk or download here. http://www.tp-link.com/en/download/TL-WN822N_V3.html#Driver

Change a channel on the main router and have a test. Try chipmaker's driver(RTL8192CU)....

Follow the guide here to enable WLAN Autoconfig. http://www.tp-link.com/en/faq-306.html