Hey !
UPDATE : It was a conflict between the plugin “Checkout Fields Manager for WooCommerce” and “Change Quantity on Checkout for WooCommerce”.
The solution :
1) Disable the plugin “Checkout Fields Manager for WooCommerce”
2) Install & activate this one “Change Quantity on Checkout for WooCommerce”
3) Reactive the plugin “Checkout Fields Manager for WooCommerce”
Bye and thanks for developing this plugin very useful !
