Laravel 5.4 : The only supported ciphers are AES-128-CBC and AES-256-CBC with the correct key lengths

I think you should try this

run this command

php artisan key:generate

and the clear config cache using

php artisan config:cache

php laravel configuration

Make sure your app config has key and cipher set. Also make sure your .env file does not have an empty APP_KEY entry. Finally run:

php artisan key:generate

php laravel configuration

Make sure to set APP_Key in .env file and then run following command in the terminal of your application root.

php artisan key:generate

CodeHunter