Hi Hank,
Apparently when you turned the inverter on you had enough juice to start the fridge, but not enough to keep it running or to keep the battery charged, even with a little juice flowing from the truck.
What may have happened is that you have lost the normal recharging from your Power Converter and the batteries were at a low charge at the beginning of the trip. If you have a volt meter, take a reading at the battery terminals while plugged into shore power, truck disconnected. If 13.2-13.6V DC, your Power Converter is recharging the batteries. If less than 12V DC, you not only have discharged batteries, but there's no power from the Converter to the batteries. Another symptom would be that internal lights and other 12V devices INSIDE the coach work when on shore power, but quit as soon as shore power is turned off or disconnected.
An alternative if you don't have a meter is to turn on the auto-leveling, if you have that, and cycle it to read the voltage.
First thing to check is the reset button on the 12V DC Mini-Circuit Breaker near the batteries. There's a row of little breakers usually covered by a red rubber boot. Two breakers usually have thick wires on the output side (battery cable goes to the input side which also has a copper buss bar connecting the breakers). One of those breakers should have a teeny-tiny very hard to see reset button. You can often find it with your fingers more easily than trying to see it. If you press that button and voltage at the batteries comes back into the 13.2-13.6 V range immediately (shore power plugged in), the breaker was tripped.
If proper charging voltage is not restored, you may have lost the output of the Power Converter. Check the main circuit breaker panel inside the coach. One by one turn each breaker off then on. Don't rely on a visual check.
If that doesn't restore charging, you'll have to check to make sure the Power Converter is still plugged in. It's usually located behind the rear wall of the basement pass through storage. If the plug has come out of the outlet, after plugging back in, tie it into place.
I'm attaching some pictures that may help you. Also, if you need to go further, you can refer to our
12V Block Diagram and Diagnostic Guide. The
Residential Refrigerator Guide has a block diagram that's closer to your setup.
I don't know if you'll need to replace the batteries. You will need to clean the terminals for sure. You may want to take them to an auto parts store or repair place and have them tested.