A common error in WordPress is an HTTP 500 error and will look something like the image below. This is not descriptive and will not help narrow down the cause of the issue. In production sites, it is best practice to show a generic error such as this one, but for the purposes of troubleshooting, we need more information.

For most users getting more information is easy.
- FTP into your website
- Open the file named wp-config.php
- Find the line where you see
define('WP_DEBUG', false);
- Change
false
to true
and save the file

The next time you refresh the page you were getting an error on you should now see more descriptive error messages which will help in troubleshooting.
If the line is already set to
true
you may have another plugin or server configuration which is suppressing the error output.