Laravel-medialibrary: Error when installing , Laravel 7

[anasmahjub1]

Class name must be a valid object or a string

at vendor/spatie/laravel-medialibrary/src/MediaLibraryServiceProvider.php:33
29| ], 'views');
30|
31| $mediaClass = config('medialibrary.media_model');
32|
33| $mediaClass::observe(new MediaObserver());
34|
35| $this->loadViewsFrom(__DIR__.'/../resources/views', 'medialibrary');
36| }
37|

[anasmahjub1]

just php artisan config:clear

[trippo]

delete bootstrap/cache/config.php