There has been a critical error on your website. – WordPress

This option started in 2019. A friendly notice something is terribly wrong with the website. You might not feel it is friendly, and terribly might be an exaggeration. But anyway you are stuck.. if you are a normal user, like an editor you should contact the person maintaining the website. If you are the owner or a developer you will have some options.

Take control

WordPress is not that harsh. An email has been send to the administrator of the site, this email has the information needed to focus on the problem. Most likely it is a plugin or a theme, if you are lucky you can still login and deactivate it or set another theme.

Hosting

If you have acces to ftp or ssh you can defenitly fix it. I prefer using wp-cli over ssh and using the command ‘wp plugin deactivate PLUGINNAME’, but you could simply delete the plugin or theme with ftp.

Debug

Since the fix could take just a minute, you might just want to turn debug mode on. This is nog enough though, you need to deactivate the WordPress handler for critical errors, which requires a new rule in your wp-config.php.. the following lines should help you:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', true );
define( 'WP_DISABLE_FATAL_ERROR_HANDLER', true );