I keep having trouble with the camera tool. Every time I try to test my video it doesn't show the animation thought the camera but shows the entire workspace. I've had this happen before and somehow got around it but it is giving me trouble again. It keeps giving me the same error report, /Applications/Adobe Animate CC 2018/Adobe Animate CC 2018.app/Contents/Common/Configuration/Camera/Flash/privatePkg/___Camera___.as, Line 450, Column 44 1046: Type was not found or was not a compile-time constant: Matrix3D. When I click on that report it says "private function getMatrix2DFrom3D(mat3D:Matrix3D): Matrix." I am not even trying to export just trying to test it but it won't let me do either.
It may help if you re-set your config (preferences) as described in this thread Can't Open Adobe Animate
esp. if you haven't tried that already.
Judging by the path in your post you are using AnCC 2018. The camera in AnCC 2019 has some significant improvements, so it may be worthwhile considering updating to 2019.
If you're not sure if you want the update, you can always install the new version while keeping the older one.
Even easier: Nest your work inside a container and don't use the camera (which can't attach to a motion guide for a curved path). That will save you a lot of frustration. You can use our movie template as an example how to do this.
I hadn't realized there had been an update and once I updated I didn't have any problems, weird but it worked.
I had this exact same problem, turns out 1 of my layers was causing the problem (in my situation it was named 'stage') so I just transferred all of its frames to another layer and deleted the layer causing the problem (layer 'stage'). this fixed it and the way I figured out this was by tinkering around with a copy of my .fla file and temporarily deleting some layers to see which one I delete would stop the problem. dear adobe, please fix all bugs with the camera tool as well as the 3d maneuver tool in the next update