Can you check you have the latest updates installed? My 3yr old keyboard one died last week, and I rang up and they said I hadn't got the updates, and when they were installed t came back to life! Worth a try..
Rebooting didn't work and Amazon have said they won't replace it, though they have offered me a discount off a new one. I'm pretty irritated though. 18 months is a crap lifespan. It was kept in a case, loved and adored. Never dropped, got wet etc. It should have survived longer than that.