WFFCO converters are not known for reliability so yes, it is possible that is it, HOwever I can think of several other possible issues as well. too many to list.
Are your HOUSE batteries in "Connected" state or are they disconnected,
Is there a tripped circuit breaker on the house battery side
or a defective one, or a blown fuse or a bad connection or wire.
What shape are the house batteries in (IE: Measure Voltage at the battery terminals) You could have a shorted cell which can cause symptoms much like what you see. (Been there I can tell you.. My somewhat heavier duty converter still provided power though)
This is a "Short list" the full list is much longer.