No Application Encryption Key Has Been Specified

From Encryption - Laravel - The PHP Framework For Web Artisans:

"Before using Laravel's encrypter, you must set a key option in your config/app.php configuration file. You should use the php artisan key:generate command to generate this key"

I found that using this complex internet query in google.com:

"laravel add encrption key" (Yes, it worked even with the typo!)

Note that if the .env file contains the key but you are still getting an application key error, then run php artisan config:cache to clear and reset the config.

In my case, I also needed to reset the cached config files:

php artisan key:generate
php artisan config:cache