Can't find a model method on production server

I have an error on production:

Method Illuminate\Database\Query\Builder::generateName does not exist.

But it works well on localhost!

Here is my Ob.php code:

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;
use Cviebrock\EloquentSluggable\Sluggable;
use Iatstuti\Database\Support\NullableFields;

class Ob extends Model {

  public static function generateName($ob) {
     // Do some stuff
  }
}

I'm calling it from controller, and got that error on production...

\App\Ob::generateName($ob);

Laravel 5.6

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