Laravel route group is not taken properly

I created 2 route groups in my api route file, and I can't access to routes of second group.

First group :

$api     = app('Dingo\Api\Routing\Router');
$request = app('\Dingo\Api\Http\Request');

$api->dispatch($request);
/* API V1 ROUTES */

$prefix = 'test';

$api->group(['prefix' => $prefix,'version'=> 'v1'],function($api) {

    $api->post('/entity/validate/{code}', [
        'as'    => 'validate.code',
        'uses'  => 'App\Http\Controllers\XXX\Api\SmsController@validateCodeV1',
    ]);
});

This is working perfectly and I reach my function validateCodeV1 that does perfectly its job. On another side I have right after it Second group :

$prefix = 'testv2';
$api->group(['prefix' => $prefix,'version'=> 'v2'],function($api) {

    $api->post('/entity/validate/{code}', [
        'as'    => 'validate.code',
        'uses'  => 'App\Http\Controllers\XXX\Api\SmsController@validateCode',
    ]);
});

Here I have a 404 when I try to call my api with a prefix testv2/entity/validate/XXX

I don't know how I can specify properly my prefix to swap from my v1 route to my v2 route... I use Laravel 5.5

EDIT : check of routes is empty, even after cache clear :

php artisan route:list | grep entity/validate
|        | POST                                   | /test/entity/validate/{code}                                                                       | validate.code                                | Closure                                                                                                    | api.controllers               |

via Chebli Mohamed