No error, no content, nothing.
WHAT IT MEANS
PHP stopped and errors are not being displayed, which is correct for production but unhelpful for diagnosis.
THE FIRST STEP
Enable error logging and reproduce. The log names the cause.
In WordPress, set WP_DEBUG and WP_DEBUG_LOG to true and WP_DEBUG_DISPLAY to false in wp-config.php, then read wp-content/debug.log.
THE COMMON CAUSES
A PHP fatal error, usually in a plugin or theme Memory exhausted A syntax error in a file that was recently edited An incompatible PHP version
ISOLATING IT WITHOUT THE LOG
Rename the plugins directory over SSH or in File Manager. If the site returns, a plugin is responsible. Rename it back and disable plugins individually.
Switch to a default theme to rule out theme code.
MEMORY
Raise memory_limit in cPanel > MultiPHP INI Editor and retest. If it resolves, something is consuming more memory than it should, which is worth investigating rather than simply raising the limit permanently.
AFTER AN EDIT
Suspect the edit. Restore your backup copy of the file.
