Not sure in your situation, since you don't list the make/model of trailer. But what I can tell you is that many slide out systems use automatic breakers. But some may use manually resettable breakers as well. The manual reset breakers have a reset button on the breaker. Just press the button and it resets. Google "resettable breakers" to see what they look like.
To find your breaker just follow your positive battery cable. It will come to a small junction usually mounted to the back wall go the storage compartment. Most generally under a red rubber cover. It is about 1/2 the size of a match book. If you pick up the rubber cover, you should see the reset button. If there is no reset button, then it is somewhere else in the system. Or else maybe the system is auto reset.
If it is auto reset you will hear it blink out when the slide out button is pressed. And about 5 to 10 seconds later, you will hear it "click" back on. If it doesn't click back on, it is either not auto reset...or it is not functioning. The good news is they are cheap to replace. About $6 at a decent auto parts store. Be sure to get the same amp rating. Ten minutes to replace.
