1990 Holiday rambler loss of power

[Meticulousmj]

My husband and I are new to RV life. We have a 1990 Holiday rambler that we have plugged into shore power, 50 amp and as soon as we plugged it into shore power at the campground, it is as though we are only getting one leg. We do not believe it’s coming from the campground pole. Struggling to find the converter and it appears that the house batteries may have gone dead (brand new, but converter inverter may have been staying on). Does anyone have any advice they can give? Back roof AC is working, front AC has stopped working and lights and outlets, washer, dryer, refrigerator, microwave have all stopped working.