How to generate token with JWT on Laravel 9 - authentication

Question

The problem is that it does not generate the TOKEN, throwing the following error
TypeError: Lcobucci\JWT\Token\Builder::relatedTo(): Argument #1 ($subject) must be of type string, null given
When I make the request through the post verb, it performs all the previous validation but when it comes to generating the token, the error occurs.
`
public function login(Request $request)
{
$credentials = $request->only('usuario', 'password');
$validator = Validator::make($request->all(), [
'usuario' => 'required',
'password' => 'required'
]);
if ($validator->fails()) {
return response()->json([
'message' => $validator->errors(),
'token' => null
], 404);
}
$user = usuarios::where('usuario', $request->usuario)->first();
if (!$user) {
return response()->json([
'message' => 'Usuario no registrado.',
'token' => null
], 401);
}
$isValid = Hash::check($request->password, $user->password);
if (!$isValid) {
return response()->json([
'message' => 'Contraseña incorrecta.'
]);
}
$token = JWTAuth::fromUser($user);
return response()->json([
'message' => 'Usuario logueado correctamente',
'token' => $token
]);
}
`
And my code mode is this
`
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
//Añadimos la clase JWTSubject
use Tymon\JWTAuth\Contracts\JWTSubject;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Laravel\Sanctum\HasApiTokens;
use Illuminate\Notifications\Notifiable;
class usuarios extends Model implements JWTSubject
{
use HasFactory, HasApiTokens, Notifiable;
protected $table = 'usuarios';
protected $fillable = [
'tipo_usuario',
'acceso_pv',
'nombre',
'usuario',
'password',
];
public function getJWTIdentifier()
{
return $this->getKey();
}
public function getJWTCustomClaims()
{
return [];
}
public $timestamps = false;
}
`