Fatal error: Uncaught Error: Class "PayPal\Common\PayPalModel" not found in /home/custom/public_html/katiekarr/vendor/paypal/rest-api-sdk-php/lib/PayPal/Api/Billing.php:18 Stack trace: #0 {main} thrown in /home/custom/public_html/katiekarr/vendor/paypal/rest-api-sdk-php/lib/PayPal/Api/Billing.php on line 18