Error- Laravel php artisan

I'm having this error when executing the command php artisan serve

RuntimeException in Encrypter.php line 43:
The only supported ciphers are AES-128-CBC and AES-256-CBC with the correct key lengths.

in Encrypter.php line 43
at Encrypter->__construct('', 'AES-256-CBC') in EncryptionServiceProvider.php line 27
at EncryptionServiceProvider->Illuminate\Encryption\{closure}(object(Application), array()) in Container.php line 746
at Container->build(object(Closure), array()) in Container.php line 644
at Container->make('encrypter', array()) in Application.php line 709
at Application->make('encrypter') in Container.php line 864
at Container->resolveClass(object(ReflectionParameter)) in Container.php line 819
at Container->getDependencies(array(object(ReflectionParameter)), array()) in Container.php line 789
at Container->build('App\Http\Middleware\EncryptCookies', array()) in Container.php line 644
at Container->make('App\Http\Middleware\EncryptCookies', array()) in Application.php line 709
at Application->make('App\Http\Middleware\EncryptCookies') in Pipeline.php line 127
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 104
at Pipeline->then(object(Closure)) in Router.php line 655
at Router->runRouteWithinStack(object(Route), object(Request)) in Router.php line 629
at Router->dispatchToRoute(object(Request)) in Router.php line 607
at Router->dispatch(object(Request)) in Kernel.php line 268
at Kernel->Illuminate\Foundation\Http\{closure}(object(Request)) in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in CheckForMaintenanceMode.php line 46
at CheckForMaintenanceMode->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 104
at Pipeline->then(object(Closure)) in Kernel.php line 150
at Kernel->sendRequestThroughRouter(object(Request)) in Kernel.php line 117
at Kernel->handle(object(Request)) in index.php line 53
at require_once('C:\xampp\htdocs\pmo\public\index.php') in server.php line 21

I have already executed the command php artisan key:generate in the app.php file I copied the generated key and put it in:

'key' => env('[base64:cDFjVAeEyMpey1sGdTBKKDAyY4ipZmOPVBeBpAsqQo4='),//

    'cipher' => 'AES-256-CBC',

In the cipher part tbm I changed by putting 128 and nothing .... I would like some tips on this problem.