This would mean that water entered and corroded/welded the two pieces. A lot will depend on the severity of the damage, if it is only the female power receptacle, this can be replaced. You will also need a new power supply most likely. The most common scenario that causes this is the power was unplugged, the male end fell in a puddle of water or the sump and was reconnected wet. The combination of electricity and salt results in heat an arcing and a very rapid corrosion which fuses and melts the parts.
Send the controller and power supply to:
Tunze USA
305 Victor St
Austin, TX 78753