Hello!
It happens to me exactly the same, and Koogeek's support tells me exactly the same thing: to change the router. But I refuse, this new one, and it's a pretty expensive Linksys.
Hue works fine, HomeBridge works fine, and I have even an Arduino programmed by me also works well with HomeKit!!!!
I have continued doing tests and I have verified that the Koogeek plugs are still connected to the wifi since they respond to Ping. The problem is that they are not able to stay connected to HomeKit. I repeat, it is not a problem of connection to the wifi but a pure problem of HomeKit.
Koogeek also tells me that I have an Apple TV problem and it does not work well with it...
Also, I turned off my Apple TV and the problems persisted. but even so, the Apple TV is by definition the center of the home automation HomeKit, so if the Koogeek plug is not able to work with it, the problem can only be due to a poor implementation of the HAP (HomeKit accessory protocol) by Koogeek.
For this reason my question is, when will we be able to download a firmware update that corrects this problem?
But I have not had an answer from Koogeek.
I do not think that a device like this is at Apple's level. it may not be worth wearing the "work with HomeKit" logo and Apple should withdraw it, because it is not true, it does not work. and they are cheating us.