If you updated your WooCommerce to version 3.3.0 (version removed by WooCommerce team the same day of publication for numerous issues) or updated to version 3.3.1 it's possible the Checkout button doesn't working as expected. Unfortunately in this update they introduced 'brutal' changes to some core files.

Please update to Uncode 1.7.3 or later versions:

• Please visit the Change Log for more informations;
• Please visit the Theme Update documentation to properly update Uncode.