All my batteries are dead

Now add to that that there may be parasitical draws that bypass the disconnect and after the battery disconnect is on for a length of time, your battery is drained. You have indicated that the battery disconnect may have been on for a while. Batteries may be permanently dead. While on inverter, they may appear good as you are reading the charging voltage. I would check my batts by turning off everything, including the charger and turn on the disconnect, for a couple hours. Then test the batts before turning on anything. Do not turn off the disconnect. You are trying to see how well the batts hold a charge.