Mine wouldn't go on initially, but can't remember what I did. I may have used fine sand paper on the pin to remove any rough spots. I did just replace my adapter with the new one that came with my AUH 3200 that replaced the rail mount model and it slipped on just fine so that supports sanding the pin. I may have contacted Andersen and did whatever they suggested which could have even been just placing the adapter where it would heat up.

 

I tried to contact Andersen but no one there on Saturday!

Just took it on a 30 mile test run and it performed beautifully!

 

I love the pin box and AUH combo. Rides so much smoother.
In case you don't know, the glide pads and rubber bolt covers are and need replacing occasionally. Also be prepared for the "paint" to flake off. I finally just flap disc and reshot it.
Also the rubber dampner is available in different grade levels, loosely based on weight. If you feel your trailer maxing out against the stops front and read you may need to go up one pad level.
The pin box is the best mood I did on our trailer, per the wife.

ZooDad

 

I didn't respond in time, but I like mine. I do notice the rubber band effect at times, but its not annoying at all.