product order not added laravel api

i am a beginner level programmer of laravel.while developing a warehouse management project i had a problem. order table table is storing successfully but product order table data is not saving.i don’t know what was the problem with code snippt . this project consist of product and client and order. order and product having a many to many relationship. can some on help me resolve the error and try to add the data into the table.what i tried so far i attached below.while tested via postmon order table data added product order table data not added

Order Controller

public function store($data)
    {

        // insert order to order table

        $order = Order::create($data);

    $products = $data['products'];

    foreach ($products as $productData) {
        $orderProduct = new ProductOrder();
        $orderProduct->product_id = $productData['product_id'];
        $orderProduct->qty = $productData['qty'];
        $orderProduct->order_id = $order->id;
        
        $orderProduct->save();

        // reduce the stock level
        $product = Product::where('id', $productData['product_id'])->first();
        $product->stock_level = $product->stock_level - $productData['qty'];
        $product->save();
    }

        return  $order;
    }

ProductOrder

class ProductOrder extends Model
{
    use HasFactory;
    protected $primary_key = "id";
    protected $table = "product_orders";

    protected $fillable = [
        'product_id',
        'order_id',
        'qty',
    ];

    public function product()
    {
        return $this->belongsTo(Product::class);
    }

    public function order()
    {
        return $this->belongsTo(Order::class);
    }
}

Order

class Order extends Model
{
    use HasFactory;

    protected $primary_key = "id";
    protected $table = "orders";


    protected $fillable = [
        'order_number',
        'total',
        'client_id',  
    ];

    public function client()
    {
        return $this->belongsTo(Client::class);
    }

    public function products()
    {
        return $this->belongsToMany(Product::class)->withPivot('qty');
    }

}

Product

class Product extends Model
{
    use HasFactory;
    protected $primary_key = "id";
    protected $table = "products";

    protected $fillable = [
        'product_code',
        'product_name',
        'stock_level',
        'price',
        'category_id',
    ];

    public function category()
    {
        return $this->belongsTo(Category::class, 'category_id');
    }

    public function orders()
    {
        return $this->belongsToMany(Order::class)->withPivot('qty');
   
    }


    
}