overload implies that the brakes are pulling too much current.
Check that the Prodigy is properly wired in your tow vehicle - if using the wiring harness adapter you need to make sure you have the right one for the right year.
Turn down the boost setting on the Prodigy and try at no boost.
Check the trailer brake wiring to make sure there are no shorts and that the wires to each magnet are in good condition and that your brake magnets are OK. - use a simple ohm meter across the brake line (may need to measure resistance in another trailer to learn what is reasonable). Then check the current when you apply 12v
to the brake line. (anyone have good reference values for typical airstream brakes for resistance and current draw?)
Check the umbilical connection to make sure you have a good ground connection between the trailer and the tow vehicle.
Good luck and happy hunting.