Error: call to undefined function – in modules/addons

Cause

This is caused by WHMCS not reading the quickbooks_sync or paypal_billing_center module hooks.php file. This is usually caused after an module upgrade that encountered an error, or a migrate from a different WHMCS install.

Resolution

You need to load our hooks file once in WHMCS, so it can realize our module is fully installed.

1. Download the hooks.php file inside the module folder inside modules/addons.
2. Upload that file into includes/hooks in your WHMCS
3. Load your WHMCS admin > Setup > Addon Modules page
4. Remove the file you uploaded into includes/hooks