Is your firmware the latest one? You can email tplink support for further analyze.

Hi Mike, did you update the kasa version and firmware version of your plug? A new firmware may help.

Is your modem working as bridge modem? A private network needs a router, maybe that's why only the first AP work. The new firmware fixed my deco's intermittent disconnection issue. You can try back...

tplink set restriction on firmware update. US version can't update EU firmware. I found QoS helped to improve video performance. maybe you can have a try. My new tplink powerline had an issue to turn...

first check the location of the kasa, maybe it is in the wrong timezone so the light turns on during the day. the device time on the light switch is the same as the led bulb? maybe you can show us...

Can your computer get IP address from the extender? http://www.tp-link.com/us/faq-838.html If the IP address is something like 169.254.XX.XX, and your brother's computer can work with that Ethernet...