Laravel/QuickAdminPanel: “the separation symbol could not be found” message when i try to confirm my email address

I activated the email confirmation in my Laravel project, when i receive the email and click the button the site return me an exception.
The code line interested is in the User Class:

<?php

namespace AppModels;

use CarbonCarbon;
use DateTimeInterface;
use Hash;
use IlluminateAuthNotificationsResetPassword;
use IlluminateContractsAuthMustVerifyEmail;
use IlluminateDatabaseEloquentFactoriesHasFactory;
use IlluminateDatabaseEloquentSoftDeletes;
use IlluminateFoundationAuthUser as Authenticatable;
use IlluminateNotificationsNotifiable;

class User extends Authenticatable implements MustVerifyEmail
{
    use SoftDeletes, Notifiable, HasFactory;

    public $table = 'users';

    protected $hidden = [
        'remember_token',
        'password',
    ];

    protected $dates = [
        'email_verified_at',
        'created_at',
        'updated_at',
        'deleted_at',
    ];

    protected $fillable = [
        'name',
        'email',
        'email_verified_at',
        'password',
        'remember_token',
        'created_at',
        'updated_at',
        'deleted_at',
        'firstname',
        'lastname',
        'address',
        'postcode',
        'place',
        'company',
        'phone',
        'mobile',
    ];

    protected function serializeDate(DateTimeInterface $date)
    {
        return $date->format('Y-m-d H:i:s');
    }

    public function getIsAdminAttribute()
    {
        return $this->roles()->where('id', 1)->exists();
    }


    public function getEmailVerifiedAtAttribute($value)
    {
        return $value ? Carbon::createFromFormat('Y-m-d H:i:s', $value)->format(config('panel.date_format') . ' ' . config('panel.time_format')) : null;
    }

    public function setEmailVerifiedAtAttribute($value)
    {
        $this->attributes['email_verified_at'] = $value ? Carbon::createFromFormat(config('panel.date_format') . ' ' . config('panel.time_format'), $value)->format('Y-m-d H:i:s') : null;
    }

    public function setPasswordAttribute($input)
    {
        if ($input) {
            $this->attributes['password'] = app('hash')->needsRehash($input) ? Hash::make($input) : $input;
        }
    }

    public function sendPasswordResetNotification($token)
    {
        $this->notify(new ResetPassword($token));
    }

    public function roles()
    {
        return $this->belongsToMany(Role::class);
    }
}

laravel exception

The problem is in the line 68:

public function setEmailVerifiedAtAttribute($value)
{
        $this->attributes['email_verified_at'] = $value ? Carbon::createFromFormat(config('panel.date_format') . ' ' . config('panel.time_format'), $value)->format('Y-m-d H:i:s') : null;
}

I try to change the timezone in the app.php but the problem still remain.
In the DB the user is registred, and can access to the website, but the field “email_verified_at” is null.