@studio90419 Hi Andre,
Thank you for the credentials, I have reopened this topic for you. A couple of potential issues that I see on the site that could be the culprit of the critical error.
First, your version of PRO is a couple of updates behind (4.1.5), please update your PRO to the latest version.
How to Perform Automatic Updates
Second, a handful of your plugins are outdated, please update all your plugins to the latest versions.
How to Properly Update WordPress Plugins (Step by Step)
Remember to clear all your caching features (plugin, server-side, CDN, and browser’s cache) after updating so that the code from the latest release is always in use. This will help you to avoid any potential errors.
Let us know how it goes,