Hello,
If you are having problems adding a product in WooCommerce, then you can refer to this article on the topic. If you continue to have issues, then please provide us more information. Are you seeing any error messages? Make a backup and then try to rebuild/reload your WooCommerce site. If you require more in depth help with WooCommerce, make sure to utilize the support information that WooCommerce provides.
If you have any further questions, please let us know.
Kindest regards,
Arnel C.