If a WHMCS site is provisioned using a product addon, there are no module commands available to control the installation once it has been provisioned. The only trick that can be performed is if the product addon status is saved as Pending and then saved again back to Active, this will cause the provisioning module to run and install a fresh copy of WHMCS for the user.
Note: This technique will run the same command as the “Provision WHMCS Site” command for standard products and will wipe out the user’s current WHMCS site.
Troubleshooting Note: If you are attempting to activate a WHMCS product addon and it will not save to Active status, this means an error is occurring during the provisioning process. Please see the Activity Log for errors.
Hosting Platform Note: The hosting platform configured for the product addon must match the hosting platform of the parent product. For example, a product addon configured for a DirectAdmin site cannot be added to a parent product that is assigned to cPanel.