You did not mention if you had a transfer sw or not. If so you might want to check it for a loose connection. Also you said your cord was good at the female end, but I have seen connections that were good at no load, but were just bad enough to not let power thru under load. One thing you can do to help verify it is between inlet and load center is to disconnect cord from trailer, put a jumper across the two hot terminals and go to the other end and ohm it out. Again it might show ok at no load but not pass power, but worth a try. Just some thoughts.