The converter is responsible for charging the battery when plugged in or on generator. It basically converts 120 volts down to 12. When charging the battery, the voltage will typically be in the mid 13s to the mid 14s.
In my Greyhawk there is a circuit breaker in the panel so that would be the first thing to check. Cycle it off and then back on. The 120 volts is fed to the converter through the breaker panel.
The converter may have fuses on it that should be checked. If the battery was hooked up backwards for a second, there usually is a fuse on the converter to protect it.
To verify that 120 volts is actually getting into your rig through the transfer switch, simply look at the microwave (if present) and see if it is lit up when plugged in or on generator. If it is on then you can eliminate the transfer switch and a few other things as your problem. If it isn't lit then your problem could be the main breaker in the panel (30 or 50 amp), a loose wire inside the transfer switch, or some other things.
Poke around and let us know what you find.
Retired electronic technician (45 years in the field)
2017 Greyhawk 29W
solar & many other mods
wife (maybe I should have given her top billing)