Cannot add or update a child row but foreign key exists

I have these two tables on my database:

And this is part of my code: Here is where I store the new complaint

public function storeComplaint($data)
{
    $complaint = new Complaint;
    $complaint->complainttype_id = $data->complainttype;
    $complaint->restaurant_id = $data->restaurant;
    $complaint->user_id = $data->vendor;
    $complaint->date = $data->date;
    $complaint->comments = $data->comments;
    $complaint->save();

    $this->storeComplaint_Product($complaint->id, $data->products); //THIS IS TO INSERT INTO THE COMPLAINT_PRODUCTS TABLE

    return $complaint;
}

This is where I store into the Complaint_Products table:

public function storeComplaint_Product($complaint_id, $products)
{
    Complaint_Product::where('complaint_id', '=', $complaint_id)->delete();

    if(!empty($products))
    {
        foreach($products as $product)
        {
            $complaint_product = new Complaint_Product;
            $complaint_product->complaint_id = $complaint_id;
            $complaint_product->product_id = $product;
            $complaint_product->save();
        }
    }
}

As you can see, when I call storeComplaint_Product I send the complaint->id and the products I want to store. still it gets me that "Cannot add or update a child row: a foreign key constraint fails" when I just created that complaint. It even shows me the information I'm trying to insert and those ids exists!!

via Chebli Mohamed