when you connect a pc to it via Ethernet cable, do you see the third light lit up? there are two ethernet ports there, have you tried both of them? it seems that there is hardware issue if the light...

not following you, as far as i know, these adapters are wall plug and have 1 ethernet cables as input or output, so they can transfer date in the powerline system. is that what you want to know?

what is the current firmware version of your adapter? And it is V1 or V2? can you show img?

i think that the cpu of it doesn't support wds so a new firmware can not do it.

do a hard reset or firmware upgrade? you can also check the signal strengthen. have you added new devices recently which may caused interference?

have you contacted TP-Link support directly? they should replace it within warranty period.