How am I supposed to make sure that the player can fall through the ground?

Using Rigidbody2D and colliders is one way it could be achieved

Does it have something to do with my code?

using UnityEngine;

public class PlayerMovement : MonoBehaviour { [Header("Movement Parameters")] [SerializeField] private float speed; [SerializeField] private float jumpPower;

 [Header("Coyote Time")]
 [SerializeField] private float coyoteTime; //How much time the player can hang in the air before jumping
 private float coyoteCounter; //How much time passed since the player ran off the edge

 [Header("Multiple Jumps")]
 [SerializeField] private int extraJumps;
 private int jumpCounter;

 [Header("Wall Jumping")]
 [SerializeField] private float wallJumpX; //Horizontal wall jump force
 [SerializeField] private float wallJumpY; //Vertical wall jump force

 [Header("Layers")]
 [SerializeField] private LayerMask groundLayer;
 [SerializeField] private LayerMask wallLayer;

 [Header("Sounds")]
 [SerializeField] private AudioClip jumpSound;

 private Rigidbody2D body;
 private Animator anim;
 private BoxCollider2D boxCollider;
 private float wallJumpCooldown;
 private float horizontalInput;

 private void Awake()
 {
     //Grab references for rigidbody and animator from object
     body = GetComponent<Rigidbody2D>();
     anim = GetComponent<Animator>();
     boxCollider = GetComponent<BoxCollider2D>();
 }

 private void Update()
 {
     horizontalInput = Input.GetAxis("Horizontal");

     //Flip player when moving left-right
     if (horizontalInput > 0.01f)
         transform.localScale = Vector3.one;
     else if (horizontalInput < -0.01f)
         transform.localScale = new Vector3(-1, 1, 1);

     //Set animator parameters
     anim.SetBool("run", horizontalInput != 0);
     anim.SetBool("grounded", isGrounded());

     //Jump
     if (Input.GetKeyDown(KeyCode.Space))
         Jump();

     //Adjustable jump height
     if (Input.GetKeyUp(KeyCode.Space) && body.velocity.y > 0)
         body.velocity = new Vector2(body.velocity.x, body.velocity.y / 2);

     if (onWall())
     {
         body.gravityScale = 0;
         body.velocity = Vector2.zero;
     }
     else
     {
         body.gravityScale = 7;
         body.velocity = new Vector2(horizontalInput * speed, body.velocity.y);

         if (isGrounded())
         {
             coyoteCounter = coyoteTime; //Reset coyote counter when on the ground
             jumpCounter = extraJumps; //Reset jump counter to extra jump value
         }
         else
             coyoteCounter -= Time.deltaTime; //Start decreasing coyote counter when not on the ground
     }
 }

 private void Jump()
 {
     if (coyoteCounter <= 0 && !onWall() && jumpCounter <= 0) return; 
     //If coyote counter is 0 or less and not on the wall and don't have any extra jumps don't do anything

     SoundManager.instance.PlaySound(jumpSound);

     if (onWall())
         WallJump();
     else
     {
         if (isGrounded())
             body.velocity = new Vector2(body.velocity.x, jumpPower);
         else
         {
             //If not on the ground and coyote counter bigger than 0 do a normal jump
             if (coyoteCounter > 0)
                 body.velocity = new Vector2(body.velocity.x, jumpPower);
             else
             {
                 if (jumpCounter > 0) //If we have extra jumps then jump and decrease the jump counter
                 {
                     body.velocity = new Vector2(body.velocity.x, jumpPower);
                     jumpCounter--;
                 }
             }
         }

         //Reset coyote counter to 0 to avoid double jumps
         coyoteCounter = 0;
     }
 }

 private void WallJump()
 {
     body.AddForce(new Vector2(-Mathf.Sign(transform.localScale.x) * wallJumpX, wallJumpY));
     wallJumpCooldown = 0;
 }


 private bool isGrounded()
 {
     RaycastHit2D raycastHit = Physics2D.BoxCast(boxCollider.bounds.center, boxCollider.bounds.size, 0, Vector2.down, 0.1f, groundLayer);
     return raycastHit.collider != null;
 }
 private bool onWall()
 {
     RaycastHit2D raycastHit = Physics2D.BoxCast(boxCollider.bounds.center, boxCollider.bounds.size, 0, new Vector2(transform.localScale.x, 0), 0.1f, wallLayer);
     return raycastHit.collider != null;
 }
 public bool canAttack()
 {
     return horizontalInput == 0 && isGrounded() && !onWall();
 }

}