The attached manual relates to our BCC, as far as I can tell.
- coach and chassis batteries are charged when plugged into shore power
- when not plugged in, chassis and coach batteries are separated at slightly above 12 VDC
- batteries need voltage for the BCC to work
I'm thinking the OP had his battery disconnect activated, which stopped the batteries charging. Something drained the batteries.
I would try charging the batteries with an external charger, and then connect everything up, plug into shore power, and measure voltage at the batteries. The measured voltage will be over 13 VDC. If the batteries won't take a charge with the external charger, new batteries will be needed as the BCC needs battery voltage.
Hope this helps!