Problem method shipping not display in cart

Hello,
I created a plugin for add new shipping method based on “flat rate” method (model for plugin here https://docs.woothemes.com/document/shipping-method-api/.

My new method is correctly display in administrator view, i can activate this but when i go in my cart i have a message “no method shipping is define”.

have you got an idea ? in cart.php the variable $available_methods is empty…

Thank you for your help

https://wordpress.org/plugins/woocommerce/