Try a reboot of the local router and Sub and then try the Sub setup again. If you have an ‘Airtime Fairness’ feature on your router perhaps try with that switched off. Also note that a Sub will not bond to some Sonos devices, like the Sonos Move.

Vous voudrez peut-être poster ceci sur le forum en Français, la plupart des gens de ce forum ne lisent pas la langue.
 

Like me, some of us use Google translate semi-efficiently, but you’re most likely to get good answers like Ken’s in the other forum, in French.