Other than swapping the lead / plug, and assuming you are not qualified to (or don’t want to) open the device there is not much you can do.  Sonos do not offer any kind of repair service, however if you call them they are usually able to offer a discount on a new purchase.  

same here, bought/installed a pair of fives two days ago. One of them is now dead. incl. no response when applying factory reset procedure. Did notice that playback wasn't all that stable after installing; actually thought the new app was to blame… Since it's a pair, I doublechecked with the other cable, no change.