My symfony application (3.4.8) seems to ignore any attempts to prolong the session. What would be the best course of action to troubleshoot this issue? The documentation is very vague.
app/config/security.yml
security:
    encoders:
        FOS\UserBundle\Model\UserInterface: bcrypt
    providers:
        fos_userbundle:
            id: fos_user.user_provider.username
        main:
            pattern: ^/
            form_login:
                provider: fos_userbundle
                csrf_token_generator: security.csrf.token_manager
                default_target_path: /
            logout:       true
            anonymous:    true
            remember_me:
                secret:   '%secret%'
                lifetime: 28000
                path:     /
            access_denied_handler: app.security.access_denied_handler
config.yml
framework:
    lock:   'semaphore'
    #esi:             ~
    #translator:      { fallbacks: ["%locale%"] }
    secret:          "%secret%"
    router:
        resource: "%kernel.root_dir%/config/routing.yml"
        strict_requirements: ~
    form:            ~
    csrf_protection: ~
    validation:      { enable_annotations: true }
    #serializer:      { enable_annotations: true }
    templating:
        engines: ['twig']
    default_locale:  "%locale%"
    trusted_hosts:   ~
    trusted_proxies: ~
    session:
        handler_id:  session.handler.native_file
        save_path:   "/tmp"
        cookie_lifetime: 28800
    fragments:       ~
    http_method_override: true
    assets: ~