Check the 12volt output at the inverter and see if it is charging. Should be around 13.8 volts. If not check the fuse. If you are getting charging voltage start tracing circuits back to the batteries. Hopefully it is a fuse and not the Xantrex itself.
If the Xantrex is defective I would be interested in purchasing it for parts. Mine still inverts but does not charge. I have a 120 volt input problem internally with it. I installed a 50 amp converter charger in mine and it charges the batteries fine.
Does the amber batteries charged light come on?