Why is the class not visible from the vendor folder?

Question

Yii

Installed the unisender package via composer, specified use Unisender\ApiWrapper\UnisenderApi in the controller; namespace in controller - namespace frontend\controllers; when instantiating $result= new Unisender() FATAL occurs: invalid class name Unisender\ApiWrapper\UnisenderApi screenshot attached below. Also in the console there was a 500 error with the text that the script is trying to access the frontend\controllers\Unisender\ApiWrapper\UnisenderApi class, although it is in the vendor folder

Answer 1

\Unisender\ApiWrapper\UnisenderApi?