Trailer ball hitch won't release

[TapOut64]

I have a brand new Wesco trailer that is only 2 months old and I am having a problem getting the hitch to release from the ball. The day I brought it home it seemed to work fine but since then has been a real problem. I've tried different ball heights and currently when hooked to my vehicle the trailer is level. The dealer said to loosen the hitch nut by half a turn which I did with no improvement. I have to jump on my bumper while my wife cranks to get it to release. I even tried a different ball. Any ideas?