How old are the tablet and the dock? Batteries don't last forever, and if this Transformer has been heavily used for a couple of years, it's possible that the batteries may not be able to hold a charge any more. Still, it's odd that it's both the tablet and the dock. How do you know the dock won't charge? Have you tried charging the dock separately? If the dock holds a charge but you're still unable to charge the tablet, then there could also be a problem with the power input for the tablet.