Welcome, You've got a few things going on in your setup that are creating problems.
Start by hiding everything that isn't connected to the camera movement.
You've got an errant Keyframe leftover from a previous 'Follow Path' Constraint on the camera. Select the camera and delete that in the Timeline.
If you open the Output Properties tab, you've changed the Time Stretching values. Reset these both to 100.
Select the Bezier Curve / Path and open the Object Data Properties Tab. Under Path Animation change the Frames value to 1000 to match what you've set as the clip length in the Timeline. You might also want to select Clamp to restrict the movement to the end points of your path.
Now add your 'Follow Path' Object Constraint to the camera, and set the target to Bezier Curve. Drag it above the Track constraint in the stack. Reset the location values of the Camera to 0 and it will locate the camera at the beginning of your curve/path.
You might also want to change the Frame count for your Nurbs Path under the Path Animation settings.
Notice that the Offset Value in the settings for your Follow Path constraint correspond to frame number and if you click and drag the value it will move the camera along the path.
Select Clamp to restrict the movement to the end points of your path.
Press Shift + L-Arrow to set the Timeline at Frame 1.
Set this Offset value to -1000. Keyframe it by pressing the button to the right of the Offset Value, this will change into a diamond shape.
Press Shift + R-Arrow to set the Timeline at the last frame (Frame 1000). Change the Offset value to 1000. And Keyframe it.
It should work now.
Alternatively, you can add the Follow Path constraint to your Empty Cube, and either Parent your Camera to the Empty or add a 'Child Of' constraint to the camera and target it to the Empty.
Hope that helps, if you find it's still not working, it should be one of those various settings that needs adjusting to make it work.