I also tried every possible way of exporting something that could animate in After Effects that retained the 3D aspects.
Anytime I did that, the 3d image went 'flat' again.
I don't seem to know what to export from PS that AE will accept and then allow me to animate.
Two parts to the answer:
1. Photoshop 3D key-frames.
If you are using Photoshop CC2018 then you have hit a bug that had been resolved in CC2017 but has re-appeared. It affects keyframes for the 3D camera (moving the the mesh works fine). There is a simple workaround though.
a. Switch on the key-frames
b. Move the timeline cursor to the next position
c. Move the camera - to add the next key-frame
d repeat b & c for remaining key-frames
To playback (this is the workaround) click on any 2D layer in the layers panel. Then press play. The camera should follow the movement you made. If you don't click on a 2D layer then the playback does not work.
You will then need to Render the video as normal using Render Video at the drop down menu at the top right of the timeline. Allow some time for this as the 3D layer is rendered for each frame.
2. If you would rather create the movement in After Effects, then export the object model using 3D > Export 3D layer - the default Collada *.dae format works fine.
Then In After Effects open Cine 4D and open the model from there. You can then control it's movement and render it in AE.