HELP ME PLEASE

Check if you are using the correct parenting method use "Parent and Link" instead of "Track Matte," as the latter can make layers invisible. Also, check that both the tracking solid and the 3D object have their visibility (eye icon) enabled and that both layers are set to 3D mode.

If the 3D object vanishes after parenting, reset its position, rotation, and scale to align it properly with the tracking data. Another common cause is an incompatible renderer try switching from Ray-traced 3D to Cinema 4D in the composition settings.

You can also check if your composition settings, including frame rate and resolution, are correctly configured. Keeping After Effects updated can also help, as newer versions fix known bugs.

Camera Tracker makes enormous values for its 3D space.  I can see in your second image that the null has shifted to the green square but is now tiny.  My guess would be that the 3D object's new position property (now that it is a child of the plane) has it either off screen or underneath or similar.  If you are using Element3D, then I've noticed this happens more frequently.

First thing to check: did you set a Ground Plane and Origin (immediately after tracking, select three points on the ground, then right-click and choose Set Ground Plane and Origin.).   Then you can create additional nulls and a camera.  

Then I like to use a free script from workbench.tv to reduce the distances.  https://workbench.tv/freebies/2020-05-28_NormalizeTrack/

And then with 3D objects everything should be more manageble.

Alternatively, if you copy the null's position values to your 3D model, does it appear?

Hi @anderson_2418,

Thanks for the message. I understand that you've tried several solutions. That sounds very frustrating. Is one of them pre-comping the 3D object and then parenting? I hope that works for you. I apologize if you've already tried that. What kind of file is this? Has this worked for you before? I hope we can help you.

Thanks,

Kevin