" They also have a few of the DC 110v outlets in their motorhome that are not working...but other ones are"
You meant AC outlets. If they were not on the same AC circuit and its breaker the converter is, then they might still not be working. OTOH, sometimes they put the converter in to share a circuit with some outlets.
But what popped the breaker? It could happen again soon without knowing what did it that time.
If a sharing situation maybe they ran a hairdryer in one of those outlets at the same time as the converter was running full on? Some reason.