error ajax laravel 405 method not allowed

I try to insert data in database with Ajax, but it doesn’t work
Error:
POST http://127.0.0.1:8000/%7B%7Broute(‘achats.store’)%7D%7D 405 (Method Not Allowed)
Controller:

$achat = new achat();
    $achat->libellé=$request->input('libll');
    $achat->date_achat=$request->input('achatDate');
    $achat->montant_total=$request->input('montant');
    $achat->Agent=Auth::user()->id;
    $achat->fournisseur=$request->get('frn');
    if($request->file('bon')){
        $bon=$request->file('bon');
        $achat->bon=$bon->getClientOriginalName();
        $bon->move('bon',$bon->getClientOriginalName());
    }
    $achat->save();
       
           return response()->json([
               'status'=>true,
               'msg'=>'Sauvegardé avec succès'
           ]);
        
    
            return response()->json([
                'status'=>false,
                'msg'=>'Le sauvegarde a échoué veuillez réessayer'
            ]);

Code js:

   $("#btn_submit").click(function(e){
   e.preventDefault();
   $.ajax({
     type:'POST',
     url:"{{route('achats.store')}}",
     data:$("#frm_add").serialize(),
     success: function(date){

     },error : function(reject){

     }
   })

})