Yes. You can have bad sockets. You can also have interference noise from various devices.

have you tried the utility or trying to connect via entering device ip?

Unfortunately, there is no conclusive answer I can provide. Sometimes, powerline adapters will work across multiple circuit breakers and sometimes they will not. If they do, they will likely have...

It depends on your PC settings. Often this is something that can be configured within system bios. You can have both wifi and lan connection or your computer can disable wifi when ethernet cable...

http://forum.tp-link.com/showthread.php?3666-how-to-solve-some-powerline-adapters-can%92t-be-waked-up-by-some-network-adapters

I am not sure why exactly you turn it off every day. There is a built in power-save function. Have you added any new appliances since the drop in connection speed?