Hi @dado4497
We’re sorry to hear that you’re encountering this issue with the Duplicate Post plugin. 500 errors generally point to an issue on the server-side. A?504 Gateway Timeout Error?indicates that a web server attempting to load a page for you did not get a timely response from another server from which it requested information.
Often, we see problems occur in combination with another plugin or theme. The fastest way to rule out any conflict, is to deactivate all non-Yoast plugins and switch to a standard theme like Twenty Twenty.
Please test this on your development or staging site, if you have one. If not, we recommend using the Health Check & Troubleshooting plugin. This plugin has a troubleshooting mode, which does not affect normal visitors to your site.
If you’re unfamiliar with checking for conflicts, we’d like to point you to a step-by-step guide that will walk you through the process: How to check for plugin conflicts
If you were to test this with a default WP theme (such as TwentyTwenty) and only WooCommerce and Yoast Duplicate Post as the plugins enabled, does it still cause the 504 errors when you attempt to clone a WooCommerce Product and does it specifically occur only with that product with 20 variations associated to it?