In order to debug for incompatibility please try the following steps:

  1. Backup your site, I advise the usage of UpdraftPlus so that you can easily restore the DB to the previous state once discovered the issue.
  2. Deactivate all plugins, except WooCommerce and Smart Variations Images PRO and test the system.
  3. If if works then start activating the other plugins one by one until the issue returns, that way you know what plugin is causing the issue (maybe plugin is not updated or not compatible with WooCommerce)
  4. Does your system have the minimum requirements?
    • PHP 5.6.30 or later – Recommended PHP 7+
    • WordPress 4.0 or later
    • WooCommerce 3.0 or later
  5. In extreme cases try changing the theme.
    1. If is theme related please open ticket so that I can further investigate, please allow me to access your system (both the WordPress dashboard and your back-end via FTP).