This guide will explain and help resolve many of the most common error messages that can occur whilst using WHMCS. Before contacting support please run through this step-by-step guide as you may be able to resolve the matter yourself.
Sometimes issues are identified between releases and individual patches are published outside the update structure which can be applied if you are experiencing the symptoms. Please review the Bug Reports Forum as a solution for your issue may already be available.
Module Command/Registrar Error
Module Command Errors are errors returned from the module and not WHMCS, so for provisioning modules (cPanel, Plesk etc) they come from your server, for registrar modules (eNom, ResellerClub etc) they come from your domain registrar.
Therefore to discover the cause of such errors refer to your server/registrar's documentation or support team. We have collected some of the most most common errors and their causes, refer to the appropriate page in the following sections:
Once the necessary corrections have been made use the Module Command buttons under the client's Products/Services or Domains tabs to attempt the command again.
Sometimes the module returns an error WHMCS does not recognise and this can result in an Unknown Error message. In these cases the System Module Debug Log should be used to obtain the full response from the module. This will contain an error message that the server/registrar's documentation or support team will be able to explain.
Blank/Partially Loading Page
If at any time you encounter a blank page in the WHMCS system ensure display_errors is enabled in the server's PHP configuration and enable the Setup > General Settings > Other tab > Display Errors option, then reproduce the blank page problem.
You should now see an error output to the screen. We have collated some of the most most common errors and their causes, refer to the appropriate page in the following sections:
If you are unable to access the admin area to enable this option, please refer to the Blank Pages documentation for further troubleshooting steps.
Payments Not Recorded
Should a payment not be recorded in WHMCS the first thing to check are the callback settings on your payment gateway's website to ensure it is configured to communicate with your WHMCS installation. As a rule callback commands should be sent to the appropriate file in the /modules/gateways/callback directory but specific instructions for individual gateways can be found at Payment Gateways.
If the configuration is correct navigate to Billing > Gateway Log and review the debug data at the time payment was made, this should display an error message or code which your payment gateway's documentation or support team will be able to explain. We have also collected some of the most most common errors and their causes, refer to the appropriate page in the Payment Gateways section.
If there is no log entry at-all and you are using a merchant gateway this suggests that the client has no card details on file.
Otherwise it means your gateway is unable to communicate with the callback file on your server, a server setting such as the firewall or mod_security could be blocking them. Liaise with your payment gateway and server administrator to resolve such matters.