symfony 4 app engine deploy Attempted to load class "Kernel" from namespace "App"

Error below not occuring on local machine, sounds like PSR issues but PSR if correctly configured

Attempted to load class "Kernel" from namespace "App". Did you forget a "use" statement for "Symfony\Component\HttpKernel\Kernel"

Autoload in composer file

"autoload": {
        "psr-4": {
            "App\\": "src/"
        }
    },

Symfony version 4.3