JWTAuth always returns false in Laravel 6 - authentication

Question

I want to create a Laravel 6 backend with JWT authentication and when I want to sign in a user, JWTAuth always returns false, I google it but can't find any solution for it.
here are my project files codes,
this is my UserController
<?php
namespace App\Http\Controllers;
use App\Http\Requests\UserRequest;
use App\User;
use Illuminate\Http\Request;
use Tymon\JWTAuth\Exceptions\JWTException;
use Tymon\JWTAuth\Facades\JWTAuth;
class UserController extends Controller
{
public function signup(Request $request)
{
$user = new User();
$user->name = $request->input('name');
$user->email = $request->input('email');
$user->password = $request->input('password');
$user->save();
return response()->json(['message'=>'User Created Successfully!',$user],201);
}
public function signin(Request $request)
{
$credentials = [];
$credentials['email'] = $request->input('email');
$credentials['password'] = bcrypt($request->input('password'));
try{
if(!$token = JWTAuth::attempt($credentials)){
return response()->json(['error'=>'Invalid Credentials!'],401);
}
}catch(JWTException $e){
return response()->json(['error' => 'Could Not Create Token!'],500);
}
return response()->json(['token'=>$token],200);
}
}
User Model
<?php
namespace App;
use Illuminate\Contracts\Auth\MustVerifyEmail;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Illuminate\Notifications\Notifiable;
use Tymon\JWTAuth\Contracts\JWTSubject;
class User extends Authenticatable implements JWTSubject
{
use Notifiable;
/**
* The attributes that are mass assignable.
*
* #var array
*/
protected $fillable = [
'name', 'email', 'password',
];
/**
* The attributes that should be hidden for arrays.
*
* #var array
*/
protected $hidden = [
'password', 'remember_token',
];
/**
* The attributes that should be cast to native types.
*
* #var array
*/
protected $casts = [
'email_verified_at' => 'datetime',
];
/**
* Get the identifier that will be stored in the subject claim of the JWT.
*
* #return mixed
*/
public function getJWTIdentifier() {
return $this->getKey();
}
/**
* Return a key value array, containing any custom claims to be added to the JWT.
*
* #return array
*/
public function getJWTCustomClaims() {
return [];
}
public function setPasswordAttribute($password)
{
if ( !empty($password) ) {
$this->attributes['password'] = bcrypt($password);
}
}
}
And Api Route
<?php
use Illuminate\Support\Facades\Route;
/*
|--------------------------------------------------------------------------
| API Routes
|--------------------------------------------------------------------------
|
| Here is where you can register API routes for your application. These
| routes are loaded by the RouteServiceProvider within a group which
| is assigned the "api" middleware group. Enjoy building your API!
|
*/
Route::post('/user','UserController#signup');
Route::post('/user/signin','UserController#signin');
when I want to sign in a user, JWTAuth:attempt($credentials), I don't know what I am missing or wrong?
Is there any solution?