Hi there ?? !
It seems that there is a conflict between WooCommerce and WP Viral Quiz.
Let’s do the following:
Firstly, let’s check that the latest version of WooCommerce is working okay on your end.
To test this, please disable all plugins except WooCommerce and check if WooCommerce works appropriately.
If it is working okay, let’s do the following:
Disable all plugins except WooCommerce and WP Viral Quiz and test again to check if they are working okay.
If still not working, change your theme to the Storefront theme, and try again to see if that works.
In case that both of the solutions provided above did not work, please contact the plugin WP Viral Quiz (by Great Reboot) support team commenting on them about the issue. Here is a link to their site:
https://gplberg.com/product/wp-viral-quiz-great-reboot/
Regardless of that, you can always rollback any plugin by using the WP Rollback plugin.
Before you start
First, please make sure you have a good backup in place of your full site and database. Most hosting companies have this included in the subscription, but you could also consider using a service like Jetpack. If something goes wrong, it’s nice to know that you can restore your site.
Second, I would suggest to install a plugin called Health Check & Troubleshooting. This is a plugin developed by the WordPress community and it allows you to disable plugins without effecting your current site visitors.
I hope this helps ! ??