[RuntimeException] No supported encrypter found. The cipher and / or key length are invalid.

[chotosite]

When I try php artisan serve it says [RuntimeException] No supported encrypter found. The cipher and / or key length are invalid.

I also tried: php artisan key:generate composer update composer install

But nothing is working

I have installed laravel 6.x. If I run laravel new blog everything is working fine.