Troubleshooting a "failed to open stream: No such file or directory' in /langupdate.php" Error
You may encounter an "Oops!" error page, and upon enabling Display or Log Errors options, the following error:
file(english.php): failed to open stream: No such file or directory' in /path/to/whmcs/lang/langupdate.php
This indicates the presence of a deprecated file in the /lang directory.
The /lang/langupdate.php file is no longer required by WHMCS and so can be safely deleted.
Once deleted, the error will be resolved.
Once the error is resolved, remember to disable Display Errors mode.