Hello @nyonyo 

Powerline units need to be plugged into the wall outlet and under the same powerline/ same power meter. 

The power strip or power extension could affect or filter the powerline signal, in that case, powerline devices may have difficulty pairing to each other or the network speed slowed down. We have guide listed some QAs that you may also get interested: 

Most frequently asked questions about TP-Link powerline devices