By default, WHMCS will hide all errors (eg PHP errors) you experience and this results in either a blank page or a 500 error from the server.
When installing new modules, it can be beneficial to test on a development server first where you can enable the display of errors.
- Login to your WHMCS server.
- Click on the Setup Tab:
- Click on Other and scroll to the bottom:
- Click on the checkbox to enable the display of errors:
- Browse the page which you were seeing issues with to see the full error output.
- Once testing or debugging is complete, Releat the process and untick the Display Errors checkbox.
For further assistance in diagnosing WHMCS errors, consult the WHMCS Troubleshooting Guide.