This message means some code on your site stopped with an error. Almost always the cause is a plugin or theme, often one that was just installed or updated.
Check your email first
WordPress usually emails your site's administrator address with the subject "Your Site is Experiencing a Technical Issue". The email names the plugin or theme that caused the error and includes a special recovery link. Open that link, log in, and deactivate the plugin or switch away from the theme it names.
If you can still log in
- Go to Plugins and deactivate the plugin you added or updated most recently.
- Reload your site. If the error is gone, that plugin is the cause: look for an update, replace it, or ask its author for help.
- If plugins aren't the cause, go to Appearance → Themes and activate a default WordPress theme (such as Twenty Twenty-Five) to test your theme.
If you can't get in
Open your site under Websites in your GUDHOST account. Under Plugins you can deactivate the plugin you added or updated most recently without logging in to WordPress; then reload your site to see whether the error is gone. If the error started right after you switched PHP version, switch back under Performance on the same page.
If that doesn't help, contact support with your domain and roughly when the error started. We'll check your site's error logs to find which plugin, theme or file is failing and help you get back in. If your site is running out of memory, we can raise its memory limit.
If the error began right after a change, we can also restore your site from a daily backup to a point before it started.