After activating the PayPal Payments module in WHMCS 8.9.0 and following the steps to link a PayPal® account, a Gateway Activation Failed error displays.

The system logs the following error details to the tblerrorlog table:

Trait 'WHMCS\Module\Gateway\paypal_ppcpv\API\RequestSendReadyAllPropertiesTrait' not found in /path/to/whmcs/modules/gateways/paypal_ppcpv/lib/API/Controller.php:0

This error is often due to the OPcache PHP extension storing a stale cache of WHMCS code.

To resolve this issue, reset the cache using the steps in the OPcache documentation.

If the issue persists, edit your server's PHP configuration to deactivate the OPcache extension.