Based on your description of "dim and beeping" it sounds like the converter is not supplying any power at all. Your battery is running down. That would explain the dim lights and the propane detector beeping on low voltage.
This condition should be easily solved by a competent RV dealer service department.
Plugged into shore power? No breakers tripped? Air conditioner working?
Chuck - Sparta, TN
2012 Jay Flight 22FB, 2 x Honda EU2000i
2013 GMC Yukon XL Denali AWD
EDUCATION is what you get when you read the fine print.....
EXPERIENCE is what you get when you don't.