Laravel my sorting filter doesn't work but i have no error or no messages

//my route

Route::get('catalogue/{categorie?}','App\Http\Controllers\CatalogueController@index')->name('catalogue');

//my function

function index($categorie = null )
    {
        if($categorie)
        {
            $products = \App\Models\Category::where('slug',$categorie)
                ->first()
                ->products()->paginate(12);

        }else{
            $products = \App\Models\Product::paginate(3);
        }   

        $categories = \App\Models\Category::all();
        $brands = \App\Models\Brand::all();

        return view('catalogue.index',compact('products','categories','brands'));
    }

//my view

<ul>
@foreach($categories as $categorie)
<li> <a href="{{route('catalogue',['slug'=>$categorie->slug])}}">{{$categorie->name}}</a> </li>
@endforeach    
</ul>

I try to display my products by category.e.g.if I click on a category, all products belonging to that category should be displayed, but they don't.I observe the URL seems works (see screen) but no matter which category I click I always have only the same 3 products so I guess category does not exist. Why and how can i fix it please ? thank you

Based on the route definition above, your route accepts categorie parameter, and not slug.

Change your route in view to this:

<a href="{{route('catalogue',['categorie'=>$categorie->slug])}}">