WaitForSeconds not working c#

Hello I am quite new to programming in unity.

I am making a pong clone.

I have set up a script that adds 1 to the score of the player on the opposing side of the board when the ball enters a trigger zone and resets its position.

However my Waitforseconds part of the code will not work. The ball just keeps moving due to the function I call after the wait for seconds code. If I take out the function the ball stops moving and just sits there. So I know that it is the Waitforseconds part.

I cannot find any solutions to this problem.

Here is my code:

 using UnityEngine;
 using System.Collections;
 
 public class scorecounter : MonoBehaviour {
 
 
     public Transform leftWall;
     public Transform rightWall;
     public float playerscore = 0f;
     public float aiscore = 0f;
     public float speed = 50f;
 
     // Use this for initialization
     void Start () {
     
     }
 
 
 
 
     IEnumerator hi (float secs){
         print (Time.time);
         yield return new WaitForSeconds (secs);
         print (Time.time);
     }
 
 
     void ResetBall() {
         var vel = rigidbody.velocity;
         vel.x = 0;
         vel.y = 0;
         rigidbody.velocity = vel;
         gameObject.transform.position = new Vector3 (0.14f, 0.5f, 0.0f);
 }
     void GoNow(){
         rigidbody.AddForce (new Vector3 (20.0f, 15.0f) * speed);
     }
     
     void OnTriggerEnter(Collider other){
         if (other.gameObject.name == "leftWall") {
             aiscore += 1;
             Debug.Log(aiscore);
             ResetBall();
             StartCoroutine(hi(2.0f));
             GoNow();
 
     }
 
         if (other.gameObject.name == "rightWall") {
             playerscore += 1;
             Debug.Log(playerscore);
             ResetBall();
             StartCoroutine(hi(2.0f));
             GoNow();
 
         }
 
 
 
     }
 
         
     // Update is called once per frame
     void Update () {
     
     }
 }