The converter portion appears to be working, because you have12V power when plugged in, however, if the charger portion is not working the symptoms will be the same.
If your model number is 63XX there is a relay in the converter output that selects whether the output goes to the distribution panel (and the battery charger), or allows the battery to feed the distribution panel when no 120vac is present (not plugged in).
Common failures are the mentioned relay, tripped CB, bad batteries or connections.
If you need schematics, just let me know.
