I bought this Kit on Amazon few days back, yesterday i got rid of the packaging, and just as it knew it, it started to play up...
The two "Clients" (Model: TL-WPA4220) have more than 300Mbit between eachother according to the tp-link utility,

but the "Master" which is connected to the router only shows 11Mbit to one client and ?Mbit to the other,... i even tried to plug them in the same double socket, tried extension cords, tried unplugging other stuff, nothing helped... I am really annoyed because they worked fine until two days ago (only bought them on 01.02.2021), and now i can't even return them cause i threw away the box.

Does anybody have a clue what i could do? i can't find any firmware, the two "Clients" seem to be fine, it seems like the master is the issue (it does not even connect to the router anymore)

please help