check if an object is reachable

Thank you for your help! The problem was in coordiates. I had different coordinates (local) for cubes and global for agent.

Here's the working script to go from one point to another. using UnityEngine; using System.Collections;

 public class randomcubepathgeneration : MonoBehaviour {
 
     //all target points
     public Transform target1;
     public Transform target2;
     public Transform target3;
     public Transform target4;
     public Transform target5;
     public Transform target6;
     public Transform target7;
     public Transform target8;
     public Transform target9;
     public Transform target10;
     public Transform target11;
     public Transform target12;
     public Transform target13;
     public Transform target14;
     public Transform target15;
     public Transform target16;
     public Transform target17;
     public Transform target18;
     public Transform target19;
     public Transform target20;
     public Transform target21;
     public Transform target22;
     public Transform target23;
     public Transform target24;
     public Transform target25;
     public Transform target26;
     public Transform target27;
     public Transform target28;
     public Transform target29;
     public Transform target30;
 
     //create array from points
     public Transform[] allpoints;
     public int randomnumber;
 
     public NavMeshAgent agent;
     public NavMeshPath path;
     public NavMeshPathStatus status; 
 
     public bool reachable = false;
     public bool hasFoundPath;
     public bool anewpath;
     public bool doonce = true;
 
     // Use this for initialization
     void Start () {
 
         allpoints = new Transform[30]; 
         allpoints [0] = target1;
         allpoints [1] = target2;
         allpoints [2] = target3;
         allpoints [3] = target4;
         allpoints [4] = target5;
         allpoints [5] = target6;
         allpoints [6] = target7;
         allpoints [7] = target8;
         allpoints [8] = target9;
         allpoints [9] = target10;
         allpoints [10] = target11;
         allpoints [11] = target12;
         allpoints [12] = target13;
         allpoints [13] = target14;
         allpoints [14] = target15;
         allpoints [15] = target16;
         allpoints [16] = target17;
         allpoints [17] = target18;
         allpoints [18] = target19;
         allpoints [19] = target20;
         allpoints [20] = target21;
         allpoints [21] = target22;
         allpoints [22] = target23;
         allpoints [23] = target24;
         allpoints [24] = target25;    
         allpoints [25] = target26;
         allpoints [26] = target27;
         allpoints [27] = target28;
         allpoints [28] = target29;
         allpoints [29] = target30;
 
         agent = GetComponent<NavMeshAgent> ();
         path = new NavMeshPath(); //without this declaration NavMesh.CalculatePath doesn't work (it doesn't even show FALSE)
         anewpath = true;
             if (anewpath = true) {
                 Debug.Log ("new target");
                 //choosing random point
                 randomnumber = Random.Range (0, allpoints.Length);
                 hasFoundPath = agent.CalculatePath (allpoints [randomnumber].position, path);
                 Debug.Log (hasFoundPath);
                 anewpath = false; //wait till the player gets to the point 
             }
         }
     
     // Update is called once per frame
     void Update () {
 
         if((path.status == NavMeshPathStatus.PathComplete) && (doonce == true));
                 {
                     print("The agent can reach the destionation");
                     reachable = true;
                     Debug.Log (status);
                     doonce = false;
 
                         if (reachable) {
                             //go to this point (the action continues even after MB was pressed)
                             agent.SetDestination (allpoints[randomnumber].transform.position);
                         }
                     
                 }
 
         if((transform.position.x == allpoints[randomnumber].transform.position.x)&&(transform.position.z == allpoints[randomnumber].transform.position.z)){
             Debug.Log ("reached destination");
             anewpath = true;
             doonce = true;
 
             if(anewpath){
                 randomnumber = Random.Range (0, allpoints.Length);
                 hasFoundPath = agent.CalculatePath (allpoints [randomnumber].position, path);
                 Debug.Log (hasFoundPath);
                 anewpath = false;
             }
 
         }
     }
 }