Polarity alarm going off!

This is my first forray into the world of shore power and I need help, when plugged in all of the electrical gadgets and lights work fine, however when I push the polarity test button on the ac panel a red light flashes and a loud alarm goes off, (usually a bad sign). The extent of my trouble shooting has been to use multiple extension cords plugged into a variety of different outlets in my garage and living room. The only time the polarity alarm has not gone off was when I used a cord that the ground terminal had broken off of the male end.Any advice would be appreciated.