Scheduler not working: No scheduled commands are ready to..

My Laravel scheduler don't work anymore, this is my kernel.php:

<?php

namespace App\Console;

use Illuminate\Console\Scheduling\Schedule;
use Illuminate\Foundation\Console\Kernel as ConsoleKernel;

class Kernel extends ConsoleKernel
{
    /**
     * The Artisan commands provided by your application.
     *
     * @var array
     */
    protected $commands = [
        //
    ];

    /**
     * Define the application's command schedule.
     *
     * @param  \Illuminate\Console\Scheduling\Schedule  $schedule
     * @return void
     */
    protected function schedule(Schedule $schedule)
    {
        $schedule->exec('echo "Done!"')->everyMinute()->appendOutputTo(storage_path('logs/Schedule.log'))->emailOutputTo('[email protected]');
        // $schedule->command('inspire')
        //          ->hourly();
        $schedule->command('telescope:prune')->daily();
        $schedule->command('synergy:sync')->everyMinute()->appendOutputTo(storage_path('logs/SynergySync.log'))->emailOutputTo('[email protected]');
    }

    /**
     * Register the commands for the application.
     *
     * @return void
     */
    protected function commands()
    {
        $this->load(__DIR__.'/Commands');

        require base_path('routes/console.php');
    }
}

I had added in my crontab:

* * * * * cd /path-to-your-project && php artisan schedule:run >> /dev/null 2>&1

With the correct path ofcourse..

When I run the command:

php artisan schedule:run

I've got the following output:

No scheduled commands are ready to run.

Is there a way to debug the scheduler? On an other Laravel project on the same server the scheduler works..