Welcome to FRF. Congrats on your new to you trailer. What model do you have?
Maybe we can help.
Parasitic drains on the trailer that are on all the time are the cause, I bet. These include Lp Detector, radio, etc. Depending on the size battery, this can happen in a week or two. A small group 24 will not last long. The cheap solution is to disconnect the neg cable. Or, install a battery disconnect.
The converter maybe under the fridge but not sure with a 2000. You'll find it where the fuses and breakers are located.
Are you getting any power at all to the AC (120 volt) appliances like air conditioning or to the receptacles?
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD