Hello,
As I see, you are using new woocommerce version and old theme version.
Please read this topic https://www.8theme.com/topic/is-royal-theme-ready-and-compatible-with-the-newest-woocommerce-3-0-update/
Don’t forget to create back up of your files and database before starting update process!
You need to enter your purchase code to activate our new theme version.
https://youtu.be/KdWESIIPU1k
(it’s for Legenda theme but the process is the same)
Please check if the problem persists with default Woocommerce theme Storefront. Also, disable all the third-party plugin and check if it fixes the issue.
Let us know the result.
Regards,
Rose Tyler.