Fatal error: Uncaught Error: Class "PKP\invitation\stepTypes\InvitationStepTypes" not found in /var/www/html/lib/pkp/classes/invitation/stepTypes/SendInvitationStep.php:31 Stack trace: #0 {main} thrown in /var/www/html/lib/pkp/classes/invitation/stepTypes/SendInvitationStep.php on line 31