What do you mean by 'applied the battery disconnect'? Did you turn it on to connect the battery to the system?
A bad battery would definitely cause the symptoms you describe. As Lakejumper said, the stabilizers are usually connected directly to the battery, and if the battery disconnect is open (off) the shore power won't power them. Once you closed (turned on) the disconnect, the converter starting charging the battery and therefore also powered the stabilizers.
Salem 29RKSS Pushing a 2500 Mega-Cab CTD!
Gotta go campin!