One of the splendours of using After Effects and Maya together is being able to import cameras from one to the other.
I use this feature a lot and then the issue came with a scene I just working on. I tried many different things and eventually realised it was the scene that was triggering the problem. I wondered if it had picked up a glitch that AE didn’t like.
So my fix was, To make a new fresh scene, import the previously exported camera (the one AE refused) then to export it again from there. Then it worked.
EDIT: Ensure that the correct resolution is set in the render settings and the camera focal length also matches the original camera.