"The page has expired due to inactivity" - Laravel 5.5

Try all of them.

composer dump-autoload
php artisan optimize
php artisan cache:clear
php artisan config:clear
php artisan route:clear
php artisan view:clear

I ran into the same issue in Laravel 5.5. In my case, it happened after changing a route from GET to POST. The issue was because I forgot to pass a CSRF token when I switched to POST.

You can either post a CSRF token in your form by calling:

 {{ csrf_field() }}

Or exclude your route in app/Http/Middleware/VerifyCsrfToken.php

 protected $except = [
        'your/route'
    ];

If you're coming to this answer directly from a search, make sure you have already added the csrf token to your form with {{ csrf_field() }} like the OP.

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If you have your session driver set to file:

May have something to do with the storage_path not being writable. This is where it stores session data regarding tokens if you're using file based sessions. The can be verified with is_writable(config('session.files'))

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For the OP, the session driver was set to array. Array is for testing only. Since data is not persisted, it will not be able to compare the token on the next request.

The array driver is used during testing and prevents the data stored in the session from being persisted.

https://laravel.com/docs/5.5/session#configuration

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Check config/session.php

Lastly, an issue I just had, we had a project which has the session domain and secure settings in config/session.php but the development site was not using HTTPS (SSL/TLS). This caused this generic error since sessions.secure was set to true by default.