How to move Groups of Objects using a Script?

Hi, I'm almost completely new to Unity, I only know the basics of everything. I recently tried to make a spaceship type thing using three game objects, that were grouped together by a parent object. However, upon applying the script, NONE of them moved. The Camera I put as a child of the actual Object, however, moves off in the intended direction by itself.

The script I used was literally the basics, and it applies properly (obviously) to a single object. What am I doing wrong?

 using UnityEngine;
 using System.Collections;
 
 public class EnergyBikeMove : MonoBehaviour {
 
     private Rigidbody rBody;
 
 
     // Use this for initialization
     void Start () {
         rBody = GetComponent<Rigidbody> ();
     }
     
     // Update is called once per frame
     void Update () {
     
     }
 
     void FixedUpdate(){
         float acceleration = Input.GetAxis ("Accel");
 
         rBody.AddForce (rBody.transform.forward * acceleration);
 
     }
 }

My Hierarchy is: EnergyBike and Cube are Probuilder cubes with Colliders.

EnergyBike has a Rigidbody which allowed it to move via that script when it was by itself, WITH the camera attached

The Camera is not the default one, but a new Camera I added.

EDIT: For some reason, even REMOVING Cube from under EnergyBike still causes the same problem. DELETING Cube completely, however, solves the problem. I don't understand . . . Upon testing with normal Unity's cubes, this problem does not exist. Is this just a Probuilder thing?