Older converters sometimes fuse the battery separate from the converter. So check all of the fuses. Plug in your power cord to shore power, switch on a couple of lights, and disconnect the ground cable from the house battery. If the lights go out or get dim, you've got a problem in the converter transformer, diodes or relay contacts. But first, check all of the AC breakers to make sure that one hasn't tripped or was shut off.
Converters are sloppy about voltage level.
When the load is low voltage is high, and vice-versa. Batteries are subject to the effects of No. 2 above. The bleed resistor is too crude to regulate voltage. Converters are not designed to recharge flat batteries or even partially discharged batteries, quickly.