How to walk on 2d sphere (planet)

Dear developers,

I have difficulties do a 2D game walking around the planet. It goes only around 90 degrees from top (where I start it) either left or right, please see the screenshot of the play. If I change the components to 3D it will work fine.

Could you please point me the error? And hopefully some fixes, too.

Player.cs:

 public float moveSpeed;
 private Vector2 moveDirection;
 public Planet attractorPlanet;
 private Transform playerTransform;
 
     void Start()
     {
         GetComponent<Rigidbody2D>().gravityScale = 0;
         GetComponent<Rigidbody2D>().constraints = RigidbodyConstraints2D.FreezeRotation;
         playerTransform = transform;
     }
     void Update()
     {
         moveDirection = new Vector2(Input.GetAxisRaw("Horizontal"), 0).normalized;
     }
     void FixedUpdate()
     {
        GetComponent<Rigidbody2D>().MovePosition(GetComponent<Rigidbody2D>().position + moveDirection);
         if (attractorPlanet)
         {
             attractorPlanet.Attract(playerTransform);
         }
     }

Player3D.cs:

 public float moveSpeed;
     public Planet3d attractorPlanet;
     private Transform playerTransform;
     private Vector3 moveDirection;
     void Start()
     {
         GetComponent<Rigidbody>().useGravity = false;
         GetComponent<Rigidbody>().constraints = RigidbodyConstraints.FreezeRotation;
         playerTransform = transform;
     }
     void Update()
     {
         moveDirection = new Vector3(Input.GetAxisRaw("Horizontal"), 0,0).normalized;
     }
     void FixedUpdate()
     {
         GetComponent<Rigidbody>().MovePosition(GetComponent<Rigidbody>().position + transform.TransformDirection(moveDirection) * moveSpeed * Time.deltaTime);
         if (attractorPlanet)
         {
             attractorPlanet.Attract(playerTransform);
         }
     }

Planet.cs (3D version is about the same: use Rigidbody instead of Rigidbody2D):

 public float gravity = -12;
     public void Attract(Transform playerTransform)
     {
         Vector3 gravityUp = (playerTransform.position - transform.position).normalized;
         Vector3 localUp = playerTransform.up;
         playerTransform.GetComponent<Rigidbody2D>().AddForce(gravityUp * gravity);
         Quaternion targetRotation = Quaternion.FromToRotation(localUp, gravityUp) * playerTransform.rotation;
         playerTransform.rotation = Quaternion.Slerp(playerTransform.rotation, targetRotation, 100f * Time.deltaTime);
     }

Thanks for your reply.