furnace/hotwaterheater wont kick on

12 volt DC fuses are normally located behind metal plate adjacent to the 120 volt circuit breakers.
Do you have a voltmeter or test light?

I assume you have a converter/charger that is contained in the power center. Saying you looked at the fuses I assume you found it. Have you actually tested the fuses, sometimes they look good but are burned out? Depending on the trailer and how it was designed the furnace and the water heater could be sharing a fuse.

Oh, also, i DO get power in the trailer when im not plugged in. The lights still work.

Ok, any idea where that is located? not in with the battery and i followed the red cable from the battery and didn't see one.

No 12 volt DC which is necessary for operation.