The you have either not inserted the charging plug fully, the charging socket is faulty, the charger is not working, or the battery has failed.
I'll assume that you're familiar enough with your headset not to have done the first option. The charging socket is probably ok if there's no obvious visible damage and it's likely that the charger is working too as they're so reliable, but you can always eliminate it as a possibility by borrowing another charger or testing the socket output against the figures printed on the charger.
But by far the most likely culprit is the built-in rechargeable battery. It's not designed to be replaceable as the complete headset is only expected to last two years, but Jabra do have a one year warranty on it: if it fails they just exchange the complete headset for a new one (or the charger if that proves faulty). Your unit can't be very old as the model is a fairly recent one, so you should first try for a repair, refund or replacement (your choice) from the retailer (a legal right under the Sale of Goods Act if you're in the UK) and then contact Jabra directly if either the retailer won't help or if Jabra has told them to refer all repair claims to them.
You'll find a link to the warranty terms
here.
