When I apply the 3d camera tracking effect, an error message appears, saying:"3D Camera tracking: layer dimension must correspond to composition and must use default transformation values" (I have translated it from italian, so the english text might not be exactly the same).
I can actually see the tracking points, but I cannot select them, like if they were part of the video. I tried using another computer, with apparently the same settings, and it works.
The composition size was likely different between the two computers or you accidentally shifted the layer in one of them.
In the computer where it didn't work, try it again. Drag your footage onto the "create new composition" button, trim your clip to the part you want to use, and then try applying the camera tracking effect.