When you plug in the converter makes the 12 volts, not the battery, when you unplug from shore power the battery makes the voltage, not the converter. The converter does the switching so it might be bad not allowing power to pass.
Only a few other components could be the cause. Verify you have a good shore power supply. Some converters plug into an outlet, make sure no GFIS are tripped. Some converters are part of the 12 volt fuse box and breaker panel, manually reset every breaker and test all the 12 volt fuses. Another component to look for is an auto breaker, these are normally located with in 18" of the battery and look like a small silver or gold box, verify that power is on both sides of that auto breaker.
Most fleetwoods do stick the converter under the fridge and are difficult to access. If everything else looks good I would suspect that converter needs to be replaced or at least have a shop check it out, it should take about 1/2 hour of labor time.
Hope this helps.
Also make sure you do not have a house dis-connect switch near the entry door, some do and some do not...
Thank You!! Please hit ACCEPT for my efforts, Positive feedback and BONUS welcomed!!