If you are facing issue like all dates are disabled on checkout page date-picker calendar then make sure pre-order days is grater than restricted pre-order days. Check the below screen-shot for a sample input.
![WooCommerce pre order and re-order restriction days settings with WooODT Extended WooCommerce pre-order date must be grater than restricted-pre-order days](https://blog.byconsole.com/wp-content/uploads/2017/12/pre-order-2-1024x459.png)
If you still have issue follow the section
D) CHECK YOUR SITE LANGUAGE
of this article