Laravel 8: Session put works but session flash does not work

I'm using Laravel 8 for my project and for updating a form and there fore in the Controller, I added this for showing success message:

Session::flash('success','asdasd');

But this does not show any data in the blade:

@if(\Session::has('success'))
<div class="alert alert-success" role="alert">
{{ \Session::get('success') }}
</div>
@endif

But when I use Session put, it shows the alert box properly:

 Session::put('success','asdasd');

However in kernel.php, I have already determined this:

protected $middleware = [
\Illuminate\Session\Middleware\StartSession::class,
...

So what's going wrong here? How can I submit the session for only one time using session->flash?

Here is the full code of session.php:

<?php
use Illuminate\Support\Str;
return [
/*
|--------------------------------------------------------------------------
| Default Session Driver
|--------------------------------------------------------------------------
|
| This option controls the default session "driver" that will be used on
| requests. By default, we will use the lightweight native driver but
| you may specify any of the other wonderful drivers provided here.
|
| Supported: "file", "cookie", "database", "apc",
|            "memcached", "redis", "dynamodb", "array"
|
*/
'driver' => env('SESSION_DRIVER', 'file'),
/*
|--------------------------------------------------------------------------
| Session Lifetime
|--------------------------------------------------------------------------
|
| Here you may specify the number of minutes that you wish the session
| to be allowed to remain idle before it expires. If you want them
| to immediately expire on the browser closing, set that option.
|
*/
'lifetime' => env('SESSION_LIFETIME', 120),
'expire_on_close' => false,
/*
|--------------------------------------------------------------------------
| Session Encryption
|--------------------------------------------------------------------------
|
| This option allows you to easily specify that all of your session data
| should be encrypted before it is stored. All encryption will be run
| automatically by Laravel and you can use the Session like normal.
|
*/
'encrypt' => false,
/*
|--------------------------------------------------------------------------
| Session File Location
|--------------------------------------------------------------------------
|
| When using the native session driver, we need a location where session
| files may be stored. A default has been set for you but a different
| location may be specified. This is only needed for file sessions.
|
*/
'files' => storage_path('framework/sessions'),
/*
|--------------------------------------------------------------------------
| Session Database Connection
|--------------------------------------------------------------------------
|
| When using the "database" or "redis" session drivers, you may specify a
| connection that should be used to manage these sessions. This should
| correspond to a connection in your database configuration options.
|
*/
'connection' => env('SESSION_CONNECTION', null),
/*
|--------------------------------------------------------------------------
| Session Database Table
|--------------------------------------------------------------------------
|
| When using the "database" session driver, you may specify the table we
| should use to manage the sessions. Of course, a sensible default is
| provided for you; however, you are free to change this as needed.
|
*/
'table' => 'sessions',
/*
|--------------------------------------------------------------------------
| Session Cache Store
|--------------------------------------------------------------------------
|
| While using one of the framework's cache driven session backends you may
| list a cache store that should be used for these sessions. This value
| must match with one of the application's configured cache "stores".
|
| Affects: "apc", "dynamodb", "memcached", "redis"
|
*/
'store' => env('SESSION_STORE', null),
/*
|--------------------------------------------------------------------------
| Session Sweeping Lottery
|--------------------------------------------------------------------------
|
| Some session drivers must manually sweep their storage location to get
| rid of old sessions from storage. Here are the chances that it will
| happen on a given request. By default, the odds are 2 out of 100.
|
*/
'lottery' => [2, 100],
/*
|--------------------------------------------------------------------------
| Session Cookie Name
|--------------------------------------------------------------------------
|
| Here you may change the name of the cookie used to identify a session
| instance by ID. The name specified here will get used every time a
| new session cookie is created by the framework for every driver.
|
*/
'cookie' => env(
'SESSION_COOKIE',
Str::slug(env('APP_NAME', 'laravel'), '_').'_session'
),
/*
|--------------------------------------------------------------------------
| Session Cookie Path
|--------------------------------------------------------------------------
|
| The session cookie path determines the path for which the cookie will
| be regarded as available. Typically, this will be the root path of
| your application but you are free to change this when necessary.
|
*/
'path' => '/',
/*
|--------------------------------------------------------------------------
| Session Cookie Domain
|--------------------------------------------------------------------------
|
| Here you may change the domain of the cookie used to identify a session
| in your application. This will determine which domains the cookie is
| available to in your application. A sensible default has been set.
|
*/
'domain' => env('SESSION_DOMAIN', null),
/*
|--------------------------------------------------------------------------
| HTTPS Only Cookies
|--------------------------------------------------------------------------
|
| By setting this option to true, session cookies will only be sent back
| to the server if the browser has a HTTPS connection. This will keep
| the cookie from being sent to you when it can't be done securely.
|
*/
'secure' => env('SESSION_SECURE_COOKIE'),
/*
|--------------------------------------------------------------------------
| HTTP Access Only
|--------------------------------------------------------------------------
|
| Setting this value to true will prevent JavaScript from accessing the
| value of the cookie and the cookie will only be accessible through
| the HTTP protocol. You are free to modify this option if needed.
|
*/
'http_only' => true,
/*
|--------------------------------------------------------------------------
| Same-Site Cookies
|--------------------------------------------------------------------------
|
| This option determines how your cookies behave when cross-site requests
| take place, and can be used to mitigate CSRF attacks. By default, we
| will set this value to "lax" since this is a secure default value.
|
| Supported: "lax", "strict", "none", null
|
*/
'same_site' => 'lax',
];

UPDATE:

public function update(Request $request)
{
$homie = HomeMainPage::where('id',1)->update([
'header' => $request->header,
'para' => $request->para,
'button' => $request->button,
'action' => $request->action,
]);
$request->session()->flash("success", "Hello, I am here");
return redirect()->back();
}

TLDR:

Ensure that the StartSession middleware is only used once for your routes.

Details:

In your question, you state that the StartSession middleware is in your global $middleware stack. However, by default, Laravel already includes the StartSession middleware in the web middleware group.

If you've added the StartSession middleware to the global stack without removing the middleware from the web middleware group, that means any routes using your web middleware group will have the StartSession middleware run twice. If the StartSession middleware is run twice, your flash data will never make it to the next request.

In the "after-middleware" part of the StartSession middleware, the session data is saved and written to storage. Part of saving the session data is aging the flash data. This moves the flash data from _flash.new (data flashed in this request) into _flash.old (flash data available in next request), and then empties out _flash.new. The next request then accesses the flash data by looking at _flash.old.

However, if the StartSession middleware is being run twice in the same request, it will end up saving the session data twice, and in turn age the flash data twice. So, on the first save it will move the new flash data from _flash.new into _flash.old and clear out _flash.new. However, in the second save, it will do this again, but since _flash.new has already been emptied, it will copy the now empty _flash.new into _flash.old, and the flash data will not exist in the next request.