I'm having a similar issue.

I was using the HS100 for a month or so without any issues. Subsequently, it developed intermittent WiFi connection issues even though nothing in the network changed. I got frustrated and removed the plug from use for some weeks.

Yesterday, I installed the smart plug near my router and upgraded the firmware to 1.2.xx (can't remember exactly). The firmware upgrade was successful and worked throughout the day. At night, I moved the smart plug to another power point, and I can't turn on the smart plug at all since. Argh!

The device worked perfectly for the first week and the suddenly it stopped working, I have the exact same issue when I activate the device it outputs power for a split second and then nothing at all. I believe the relay must be damaged or something I guess its a factory defect.

Also having the same problem. What were you all switching? I was switching a 1500 W space heater. This reddit post links to an Amazon review with more information from TP Link. IMO, stating 15 A load without qualifier is a dangerous mistake by TP Link.

https://www.reddit.com/r/homeautomation/comments/5mlgps/newbie_what_smart_plugs_can_accommodate_a_space/