If you're plugged in to shore power, the Power Converter should be providing power to the fuse box even if the 12V circuit breaker is tripped or if the battery is dead. Are other 12V appliances working? Overhead lights, scare lights, refrigerator?
Inside the fusebox, check the furnace's 12V fuse.
You might be in a safety lockout that requires a thermostat reset to get things going again. Turn the thermostat off and set the temp low enough that there's no call for heat. Wait 10 seconds and then switch back to heat and set the temp high enough to activate the furnace.
The thermostat signals a relay that's usually located with the Air Conditioner. So you may hear a click from that relay, after which the furnace blower should start. If you've reset the thermostat, and you still get no blower and no relay click, pull the cover off the thermostat to check that the wires are in place.
If the thermostat looks ok, although it's unlikely, you could have a loose connector in the relay box. To get to it, you'd remove the A/C cover on the ceiling, where the filter is located. There should be a gray box with connectors plugged in. Check the connector seating. Don't open the box unless you're very experienced working with 110V systems.
You could also have a loose wire at the furnace. But if you don't see anything obvious, at this point you'll probably have to get a service tech to look at the problem.