It's less than 1 year old so should still be under warranty with MS, shouldn't it? Mine stopped working after 3 months - the light was on the charger when plugged in but SP4 didn't recognise it. I tried it with another charger and that worked so phoned MS and explained - they sent out a free replacement and just asked me to dispose of my old charger responsibly. Took 4 days to arrive (I'm in UK, think parcel arrived from Belgium).
As I was working on something at the time it broke, I did order a 3rd party charger through
Amazon on next day delivery. Although it got me through, it wasn't very good. I render videos and while rendering, the 3rd party PSU wasn't powerful enough and I'd often lose charge until the rendering was complete.