Why this happens

A 500 error is a generic 'something went wrong on the server' message rather than a specific one. It's most often triggered by a corrupted .htaccess file, a plugin conflict, an exhausted PHP resource limit, or a file permissions issue - the vague wording is exactly why it's worth checking each common cause in order.

Step-by-step fix

  1. Back up your .htaccess file in the root folder, then rename it (e.g. .htaccess-old).
  2. Go to wp-admin > Settings > Permalinks and click 'Save Changes' without changing anything - this regenerates a fresh .htaccess file.
  3. If that doesn't work, rename the Plugins folder to disable all plugins and check again.
  4. Also try raising the PHP memory limit and execution time (see the steps above).

How to prevent it happening again