There could be other reasons that the brakes are not working like excessive grease intrusion, worn parts, broken parts, etc. Diagnosing the exact issues is difficult without lifting the trailer and pulling drums. If nothing has been done for axle end maintenance, the correct service would be to pull the hubs/drums, inspect, and service. Some of us do this on a routine basis to insure proper brake and bearing function.
What I'm having trouble understanding is that the OP states a 2003 trailer (his profile shows a 2005) and either of these would have a NADA value of > $7K with typical amenities and in fair condition. Having inoperable brakes would lower the value considerably and is a safety hazard for anyone trying to tow it.
Then again, there are some that trade in their car if the cigarette lighter breaks...