Hi!
You need to attach camera to RailCameraMount.
Try this way:
1. Place camera rig.
2. Place camera actor.
3. Attach camera to camera rig.
4. Align camera to RailCameraMount.
5. In Sequenser add Camera Rig.
6. Camera Rig -> + -> Track -> Current Position on Rail.
7. Camera Rig -> + -> Track -> RailCameraMount.
8. RailCameraMount -> + > Track -> Transform.
Useful links:
Also you can download "Sequencer" project: