Most common solution
First thing you should try is accessing WooCommerce > Status > Tools and click on Regenerate lookup tables and Clear transients .
Dealing with “0%” or “Save $0”
This can happen if a certain type of product type is not supported. With a bit of coding, custom product types can be restricted using a code like this one https://d.pr/n/AM7MiF .
Dealing with dynamic price plugins
When using a plugin that’s dynamically changing the price of the product, the way the product price is discounted, is not “friendly” with WooCommerce’s built-in is_on_sale() or get_sale_price() methods, and in Rey these are essential to calculate the discounts.
Things evolves so depending on the requests, i will try to create some sort of compatibility but it can take some time.
Disabling the internal caching mechanism
Sometimes, such as when using a multi-currency plugin, the badge might show different numbers. That likely happens because of the internal caching, and you can enable this by adding the code snippet below inside the child theme’s functions.php .