laravel：找不到支持的加密器。 密码和/或密钥长度无效

I created a new laravel application and didn't write any custome code. All I did is running the following command:

php artisan migrate

which migrated the default user table that came with laravel. and then ran the command:

php artisan make:auth

now the homepage is the default homepage of laravel but when I click on login or register I get:

RuntimeException in EncryptionServiceProvider.php line 31: No supported encrypter found. The cipher and / or key length are invalid.

still learning laravel so I want to figure out how the auth works and how to customize it. but it seems that even the default has a problem which I can't solve.

From command line enter php artisan key:generate Check solutions here: laravel No supported encrypter found. The cipher and / or key length are invalid

In config\app.php change:

'cipher' => 'whatever it is',

to

'cipher' => 'AES-256-CBC',