Hello,
1. You need to create backup of your files, database and theme options (Theme Options > Import/Export > Options > Export Options) to be able to restore the site to previous state if something goes wrong.
Please follow instructions and update theme to the latest version 3.1:
https://www.8theme.com/demo/docs/royal/#!/installation_upgrade
Also, update all required plugins: https://www.8theme.com/download-plugins/
Before uploading theme files delete “woocommerce” folder, which is located in wp-content/themes/royal/ to avoid problems with old files (it’ll be reuploaded from a new theme package).
Don’t forget to create backup of your files and database before starting update process!
You need to enter your purchase code to activate the theme and skip Setup Wizard.
2. At first, you need to update the theme, woocommerce and all plugins. If after that the problem will persist try to disable 3-rd party plugins.
3. Please read these suggestions https://www.8theme.com/reply/169282/
Regards