Several possible problems.. But first let's look at a line drawing
Converter--Display panel/fuse box----Switch---Fuse or breaker---Batteries--A few things that NEVER get shut off.
Now.. Possible issues: Some fuse boxes have some 30 amp fuses. Depending on the box ONE of them may be for the battery.. Just one (It is the fuse in the phrase "Fuse or breaker"
The switch may be OFF (Disconnected/Store) or the device the switch controls (A solenoid is a remote controlled switch) may be defective.
The fuse or breaker, mine is self-resetting but not all are, many are manual reset.
And last but not least.. bad connection, bad or broken wire.