Converter does not run

[jalad12]

2019 Cougar 27Res. On my maiden voyage! Hooked up to a 50 amp circuit at a campground. Wired for 50 but have only one A/C unit. Things seemed ok for the first two days. Running A/C during day, fridge on electric, water heater on electric/gas, and toaster oven for toast at breakfast. This morning, the third day, voltage was 11.5 and steady. We left for several hours and returned to find voltage at 8.4. I checked the converter and The 35 amp fuse was blown. The 40 amp fuse was intact. I only had a 30 amp fuse to replace with and when I put the new fuse in the fan kicked on for about 5 seconds then shut off. I removed the fuse and checked it. It was still good. I put it back in and the fan again ran for 5 seconds before stopping. This cycle happened two more times before the fan didn’t come on at all. Do I need to charge the batteries before the converter will stay on ? Do I need a new converter? In the meantime, my slide outs won’t retract and I’m not sure if the auto leveling device will work. I’m supposed to be out of the campground in 12 hours!