enemy not spotting player?

hi!can anyone help me? i am having issues with the enemy ai. whilst it does raise its gun at the player or patrol, for some reason not seem to chase the player. can anyone help me? thanks

 using UnityEngine;
 using System.Collections;
 
 public class EnemyAI : MonoBehaviour 
 {
     public float patrolSpeed = 2f;
     public float chaseSpeed = 5f;
     public float chaseWaitTime = 5f;
     public float patrolWaitTime = 1f;
     public Transform[] patrolWayPoints;
     
     private EnemySight enemySight;
     private NavMeshAgent nav;
     private Transform player;
     private PlayerHealth playerHealth;
     private LastPlayerSighting lastPlayerSighting;
     private float chaseTimer;
     private float patrolTimer;
     private int wayPointIndex;
     
     void Awake ()
     {
         enemySight = GetComponent<EnemySight> ();
         nav = GetComponent<NavMeshAgent> ();
         player = GameObject.FindGameObjectWithTag(Tags.player).transform;
         playerHealth = player.GetComponent<PlayerHealth> ();
         lastPlayerSighting = GameObject.FindGameObjectWithTag (Tags.gameController).GetComponent<LastPlayerSighting> ();
     }
     void Update()
     {
         if (enemySight.playerInSight && playerHealth.health > 0f)
             Shooting ();
         else if (enemySight.personalLastSighting != lastPlayerSighting.resetPosition && playerHealth.health > 0f)
             Chasing ();
         else
             Patrolling ();
         
         
     }
     
     void Shooting()
     {
         nav.Stop ();
         
     }
     
     void Chasing()
     {
         Vector3 sightingDeltaPos = enemySight.personalLastSighting - transform.position;
         if (sightingDeltaPos.sqrMagnitude > 4f)
             nav.destination = enemySight.personalLastSighting;
         
         nav.speed = chaseSpeed;
         
         if (nav.remainingDistance < nav.stoppingDistance) {
             chaseTimer += Time.deltaTime;
             if (chaseTimer > chaseWaitTime) {
                 lastPlayerSighting.position = lastPlayerSighting.resetPosition;
                 enemySight.personalLastSighting = lastPlayerSighting.resetPosition;
                 chaseTimer = 0f;
                 
             }
             
         } else
             chaseTimer = 0f;
         
         
     }
     
     void Patrolling()
     {
         nav.speed = patrolSpeed;
         
         if(nav.destination == lastPlayerSighting.resetPosition || nav.remainingDistance < nav.stoppingDistance) {
             patrolTimer += Time.deltaTime;
             if (patrolTimer >= patrolWaitTime) 
             {
                 if (wayPointIndex == patrolWayPoints.Length - 1)
                     wayPointIndex = 0;
                 else
                     wayPointIndex++;
                 patrolTimer = 0f;
             }
         } 
         else 
             patrolTimer = 0f;
         nav.destination = patrolWayPoints [wayPointIndex].position; 
         
     }
 }