Have you changed ethernet cables? This is really weird~ Or try to add them one by one? do they work properly?

packet.dll is an important file on windows. If there is this error, you need to download it to your computer. Then, open Start-Run and put regsvr32 packet.dll, press enter. the error will be solved....

you mean it can't display the right name which you changed on the web page? try to change that name on APP directly?

Have you changed other power sockets? how about reset or restart?

Does it can be controlled remotely via kasa app? Have you enabled kasa skill? which step do you get struck? Make sure the account you put on Alexa should be the same as the account bound on device.

if your router is still able to return , you can see homecare routers which can setup individual rules for each device. https://www.tp-link.com/us/faq-1707.html