FatalErrorExceptionClass name must be a valid object or a string

[YADeM]

Good day!
Can you help me with erros. I break my mind to find where is problem.
Trying to use your library in blank laravel project, but getting error
And get error.

FatalErrorExceptionClass name must be a valid object or a string in D:\wamp64\www\bot-app\vendor\radutopala\skype-bot-php\src\Skype\Client.php line 62

Controller

<?php
namespace App\Http\Controllers;

use Illuminate\Http\Request;
use Skype\Client;

class botsend extends Controller
{
	public function index(Request $request)
    {
		$client = new Client([
			'clientId' => 'id',
			'clientSecret' => 'secret',
			'fileTokenStoragePath' => ('./key.txt') //try with and without this string
		]);
		$api = $client->authorize()->api('conversation');   // Skype\Api\Conversation
		$api->activity('29:userid', 'Your message');
	}
}

composer.json:

{
"name": "laravel/laravel",
"description": "The Laravel Framework.",
"keywords": ["framework", "laravel"],
"license": "MIT",
"type": "project",
"require": {
"php": ">=5.6.4",
"laravel/framework": "5.4.",
"laravel/tinker": "~1.0",
"radutopala/skype-bot-php": "^1.2"
},
"require-dev": {
"fzaninotto/faker": "~1.4",
"mockery/mockery": "0.9.",
"phpunit/phpunit": "~5.7"
},
"autoload": {
"classmap": [
"database"
],
"psr-4": {
"App\": "app/"
}
},
"autoload-dev": {
"psr-4": {
"Tests\": "tests/"
}
},
"scripts": {
"post-root-package-install": [
"php -r "file_exists('.env') || copy('.env.example', '.env');""
],
"post-create-project-cmd": [
"php artisan key:generate"
],
"post-install-cmd": [
"Illuminate\Foundation\ComposerScripts::postInstall",
"php artisan optimize"
],
"post-update-cmd": [
"Illuminate\Foundation\ComposerScripts::postUpdate",
"php artisan optimize"
]
},
"config": {
"preferred-install": "dist",
"sort-packages": true,
"optimize-autoloader": true
}
}

php:

$ php -v
PHP 5.6.25 (cli) (built: Aug 18 2016 11:39:15)
Copyright (c) 1997-2016 The PHP Group
Zend Engine v2.6.0, Copyright (c) 1998-2016 Zend Technologies

OS - Windows 10 x64 build 1703, 15063.540