This question is all over stackoverflow but I just had to post it again.
Mine is actually on Fortrabbit, I've been having this error on Fortrabbit for a Laravel 5.4 App, even after I've generated the key with php artisan key:generate and in my config/app.php I have "cypher" : "AES-256-CBC".
Almost tried all it takes to fix this error, but still getting it at the end.
The only supported ciphers are AES-128-CBC and AES-256-CBC with the correct key lengths.
Is this a Fortrabbit thing? I don't know if anyone else has encoountered this on Fortrabbit Any help is appreciated.
I've done php artisan config:cache, composer install still the same.
Thanks
After debugging and testing out, the issue is with how fortrabbit handles environment variables. Apparently it ignores the .env file and sets its own default values. Or you're using git deployment which has the .env file ignored by default. To set your own values, you need to update them in their dashboard.
https://help.fortrabbit.com/install-laravel-5-uni
Just copy all your .env file content and add them in the dashboard. As an alternative you can set the values in the configuration files.