Camera won't follow path

I’ve got the path set up, and constrained the camera to it, but it’s not moving. I’d eventually like to focus the camera on an empty, but I won’t know where to put the empty in time until the camera’s moving along the path. It was working, and now it isn’t. I don’t know what I did wrong. I’d love to attach the file for anyone to look at, but it fails to upload every time I try. Is 14 MB too big? Any suggestions?

Well, I’ve gotten the path to work, but now the camera flips wildly in places along the path where I have it damping to a constraint. I don’t want any y-axis rotation anywhere in my setup; how do I get it to stay level? I couldn’t attach the file here, so I had to do it from

Replace the “Damped Track” constraint with a “TrackTo” constraint. (To: -Z, Up: Y, World Space <–> World Space)

That’s the only thing that works here.

Thank you! Thank you! Thank you! I was running out of hair to pull out.
Those settings are how I can stop the Y-axis from moving in other scenes too?

I can’t say for sure without seeing the other scenes but if they also have a camera on a path looking at an empty or another object, then yes, the “TrackTo” constraint with the same parameters will prevent the camera from rolling sideways.