range extender ineffective and too complicated to configure

Bought to boost wireless coverage apartment, I had to take me to several dozen times (and yet
I know something in network) to finally reach the end of the configuration steps via the "easy setup".
I tried on two remote PCs 50cm and 3M my neufbox SFR. The only one who was at the end stage of the setup is the PC on Vista 32-bit, the other systematically blocked at the last configuration step.
And once setup is complete, I disconnect and reconnect the RJ45 stent in another room, and there ... NOTHING :(
Call the hotline overtaxed TP-link where I fall on voicemail.
I have read the comments here and there, but hardly anyone says on
which network it is (free, sfr etc.)
From what I read it seems that change the IP class of the extenser (192.168.0.254 by default)
to correspond to the IP of the modem router (192.168.1.1 SFR).
Finally a range extender too complicated to configure, support to ch ...