Access Controller resources based on Laravel/Spatie Permissions

Question

I am working on Laravel passport api in which i am using spatie package for user role's and permission's. I have to perform certain operation ('store','view','update','delete') based on user permission's. For this purpose i have created a trait and used in controller but it is not working correctly. On every api request it throw's an exception "This action is unauthorized" either the user has permission or not.

Authorize Trait :

<?php

namespace App;
/*
 * A trait to handle authorization based on users permissions for given controller
 */

trait Authorizable
{
    /**
     * Abilities
     *
     * @var array
     */
    private $abilities = [
        'index' => 'view',
        'edit' => 'edit',
        'show' => 'view',
        'update' => 'edit',
        'create' => 'add',
        'store' => 'add',
        'destroy' => 'delete'
    ];

    /**
     * Override of callAction to perform the authorization before it calls the action
     *
     * @param $method
     * @param $parameters
     * @return mixed
     */
    public function callAction($method, $parameters)
    {
        if( $ability = $this->getAbility($method) ) {
            $this->authorize($ability);
        }

        return parent::callAction($method, $parameters);
    }

    /**
     * Get ability
     *
     * @param $method
     * @return null|string
     */
    public function getAbility($method)
    {
        $routeName = explode('.', \Request::route()->getName());
        $action = array_get($this->getAbilities(), $method);

        return $action ? $action . '_' . $routeName[0] : null;
    }

    /**
     * @return array
     */
    private function getAbilities()
    {
        return $this->abilities;
    }

    /**
     * @param array $abilities
     */
    public function setAbilities($abilities)
    {
        $this->abilities = $abilities;
    }
}

Routes:

Route::middleware('auth:api')->group(function () {
        Route::post('user', 'ApiController@user');
        Route::post('view_department', 'DepartmentController@index');
        Route::post('add_department', 'DepartmentController@store');
        Route::post('edit_department', 'DepartmentController@update');
        Route::post('delete_department', 'DepartmentController@destroy');

        Route::post('/logout', 'ApiController@logout');
    }); // auth middleware ends

Controller:

<?php

namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;
use Carbon\Carbon;
use App\User;
use App\Authorizable;
use Illuminate\Support\Facades\Validator;
use App\Department;
use Spatie\Permission\Models\Role;
use Spatie\Permission\Models\Permission;

class DepartmentController extends Controller
{
     use Authorizable;

        //
    public function index(Request $request) {

        // return response
        return response()->json([
            'success' => 'You have the permission to view departments!']);
    }

    //
    public function store(Request $request) {
        // validate the posted data
        $validator = Validator::make($request->all(), [
            'name' => 'required|string|unique:departments',
        ]);
        // return errors
        if ($validator->fails())
        {
            return response(['errors'=>$validator->errors()->all()]);
        }

        $department = new Department;
        $department->name = $request->name;
        $department->save();

        // return response
        return response()->json([
            'success' => 'Successfully created department!']);
    }
}

I am badly stack at it, don't know where i am going wrong. I would highly appreciate if anyone guide me through this. Thanks,