I know this may sound stupid, but did you bring the RPMS up with the gas as you were checking both charge and voltage? The generator will typically not charge at low idle.
When I got my wiring harness, the schematic was incorrect and had the amp meter hooked up backwards.
I have also had odd thing happen with old batteries where they would not show a charge at the gauge. I would for sure borrow a known good battery from your car and try that before I did anything else.
Kurt
