On my Chateau 28Z, the shore power charger is disconnected from the batteries (both house and chassis) when the battery disconnect is set to "store". You can check with a volt meter across the house batteries; when the battery disconnect switch is in store, you would show a voltage of ~12.3 and a voltage between than 12.7 and 14.2 with the disconnect switch in "Use" (or connected...) and on shore power. If voltage is the same regardless and below 12.5, then check the fuses and breakers. Hopefully the solution is that simple.
One other note; the CO and propane detector and one radio draw power at about 1/2 amp from the house batteries whenever the switch is connected. Neither can be turned off independently.