@vanoo,

After the update of WooCommerce 3.3.1 the prices of products aren’t showed anymore in the category archive page, neither the option to place a product in your cart.

This is more than likely caused by either a conflict with your theme or with another plugin.

The best way to determine if the issue is being caused by a theme and/or plugin is to temporarily switch your theme to Storefront and disable all plugins except for WooCommerce. If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you while you’re logged in to that session without affecting normal visitors to your site. Note that Health Check may not count Storefront as a default theme, so you can also use Twenty Seventeen as well.

If that resolves the issue, then one-by-one you can switch back your theme and re-enable your plugins, testing in between, until you find the one causing the conflict.

I had modified template files in the older version of WC in yourtheme/woocommerce/ etc, but when I updated WC then those files where changed or even gone! This is something that should not happen right?

Were the modified templates placed in a /woocommerce directory inside your active theme? That’s where they need to be to be safe from upgrades. If they were in such a folder and are now gone, that could be as a result of an old full site backup being restored or something of the sort. It certainly wouldn’t have been as a result of updating WooCommerce and even updating your theme should spare that folder.

> And about the replaced files of WC, I don’t know what happend then, because the files were in wp-content/themes/mytheme/woocommerce/.. And we did not restore any old backup

That’s strange that they disappeared. Unless instead of modifications in the theme directory, they were modified directly in WooCommerce.

It’s recommended to save these files in a safe place (if you find them) before updating your theme as they could be wiped out with an update.