I didn't find your post until just now. Sorry! If you put in your reply, then I get a notification of a reply and it is very easy to find your post as soon as you post it and I log on. I will look at your model now.
Also, please reply with the version of ANSYS you are using.
First mistake I found, Large Deflection is Off. This is a Large Deflection problem, turn that On.
Second mistake I found, the Contact with the bump is Far Open. That means it will not be used! You need to increase the Pinball radius until it is Near Open. Another mistake is the wheels are not touching the ground. I added an offset to get that.
I recommend you change the way the point mass connects to the structure. You had a Rigid connection, you should use a Deformable connection. It will be more efficient solving if you just pick 4 edges instead of 2 faces because there will be fewer nodes in the connection.
Another issue is meshing with linear elements and having only one element through the thickness such as the wheel holder. That makes that part stiffer than reality, but can probably remain.