New carrier module works only in free shipping

[stathis88k]

I have a strange problem with a new module I develop. The module install's a new carrier. I want to use the default prestashop's configuration for shipping. That means in the back office the admin can enter the prices, weights etc like a normal carrier.

 

The problem is that when I put price, the carrier doesn't appear in the shipment page in front office as an option when you make an order. It only appears when I put the carrier in free shipping. 

 

Does any body know why this is happening?

 

I followed this tutorial http://www.prestashop.com/blog/en/carrier_modules_functions_creation_and_configuration/ .

 

The example works fine but my implementation not. The only difference with the above is that I just return the shipping cost. Here are my functions.

public function getOrderShippingCost($params, $shipping_cost)
    {
        return $shipping_cost;
    }

    public function getOrderShippingCostExternal($params)
    {
        return false;
    }

Edited September 5, 2014 by stathis88k (see edit history)