Sounds like SIL fitted a range extender, not a powerline adaptor, a powerline adaptor would be almost full strength signal, but would need cable to laptop/PC not wifi.
They do work well, I have one in the living room, other end to the router, saves trailing a cable,plus one in the workshop about 150 feet away at the end of the garden, works with no weakening of signal. Wherever there is a 3 pin plug you can have a powerline adaptor.
A range extender on the other hand can sill be foiled and needs optimum conditions to be worthwhile.
Ideally a full system and cabling check and firmware updating is the right way to start.
Good Morning Friday 25th April 2024
Angela Rayner lashes out and calls Sunak “pint sized loser”.