hitch doesn't fit

Hello OP. I have had the same problem except with a well used lance TT. This wasn't my first trailer and not, as they say, my first rodeo. I cussed as well as I knew how but to no avail, so out came the hammer. A few taps and it was on but was just as difficult getting off. I knew something wasn't right but couldn't get it through my thick head. I cleaned out all the crud and gook that had built up in the tongue and still ran into the same problem. It turns out the tongue lock that engages the ball wasn't moving back far enough. My answer and eventual fix was dousing the whole works in WD40 to clean and then a coating of spray lithium grease. The mechanism was so dried up and dirty that it wasn't fully disengaging. The lubricants did their job and now hitching is easy, as it should be. Good luck with the lubricants. Spray well up into the mechanism and don't forget to grease the ball and any other parts of the WDH that call for it.